diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 31c926233d5b6..ffe615a63b7e3 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -4,7 +4,7 @@ repos:
     hooks:
     -   id: black
 -   repo: https://gitlab.com/pycqa/flake8
-    rev: 3.8.4
+    rev: 3.9.2
     hooks:
     -   id: flake8
         additional_dependencies: [flake8-comprehensions>=3.1.0]
diff --git a/ci/azure/posix.yml b/ci/azure/posix.yml
index 4cb4eaf95f6f5..2bb348a11655c 100644
--- a/ci/azure/posix.yml
+++ b/ci/azure/posix.yml
@@ -62,7 +62,7 @@ jobs:
           ENV_FILE: ci/deps/azure-38-numpydev.yaml
           CONDA_PY: "38"
           PATTERN: "not slow and not network"
-          TEST_ARGS: "-W error"
+          TEST_ARGS: "-W error -W \"ignore:Promotion of numbers and bools:FutureWarning\""
           PANDAS_TESTING_MODE: "deprecate"
           EXTRA_APT: "xsel"
 
diff --git a/ci/deps/actions-37-cov.yaml b/ci/deps/actions-37-cov.yaml
index 5381caaa242cf..5d9ba70e37307 100644
--- a/ci/deps/actions-37-cov.yaml
+++ b/ci/deps/actions-37-cov.yaml
@@ -15,8 +15,8 @@ dependencies:
   - beautifulsoup4
   - botocore>=1.11
   - dask
-  - fastparquet>=0.4.0
-  - fsspec>=0.7.4
+  - fastparquet>=0.4.0, <=0.5.0
+  - fsspec>=0.7.4, <2021.6.0
   - gcsfs>=0.6.0
   - geopandas
   - html5lib
@@ -30,7 +30,7 @@ dependencies:
   - openpyxl
   - pandas-gbq
   - google-cloud-bigquery>=1.27.2 # GH 36436
-  - psycopg2
+  - psycopg2=2.8.6
   - pyarrow>=0.15.0
   - pymysql<0.10.0 # temporary pin, GH 36465
   - pytables
diff --git a/ci/deps/azure-37.yaml b/ci/deps/azure-37.yaml
index 4fe3de161960c..13b46b4d28828 100644
--- a/ci/deps/azure-37.yaml
+++ b/ci/deps/azure-37.yaml
@@ -14,8 +14,8 @@ dependencies:
 
   # pandas dependencies
   - botocore>=1.11
-  - fsspec>=0.7.4
-  - numpy
+  - fsspec>=0.7.4, <2021.6.0
+  - numpy=1.19
   - python-dateutil
   - nomkl
   - pyarrow=0.15.1
diff --git a/ci/deps/azure-windows-37.yaml b/ci/deps/azure-windows-37.yaml
index e7ac4c783b855..dd67d9a9c1177 100644
--- a/ci/deps/azure-windows-37.yaml
+++ b/ci/deps/azure-windows-37.yaml
@@ -15,7 +15,7 @@ dependencies:
   # pandas dependencies
   - beautifulsoup4
   - bottleneck
-  - fsspec>=0.8.0
+  - fsspec>=0.8.0, <2021.6.0
   - gcsfs>=0.6.0
   - html5lib
   - jinja2
diff --git a/ci/deps/azure-windows-38.yaml b/ci/deps/azure-windows-38.yaml
index 661d8813d32d2..fdea34d573340 100644
--- a/ci/deps/azure-windows-38.yaml
+++ b/ci/deps/azure-windows-38.yaml
@@ -15,7 +15,7 @@ dependencies:
   # pandas dependencies
   - blosc
   - bottleneck
-  - fastparquet>=0.4.0
+  - fastparquet>=0.4.0, <=0.5.0
   - flask
   - fsspec>=0.8.0
   - matplotlib=3.1.3
diff --git a/ci/deps/travis-37-arm64.yaml b/ci/deps/circle-37-arm64.yaml
similarity index 100%
rename from ci/deps/travis-37-arm64.yaml
rename to ci/deps/circle-37-arm64.yaml
diff --git a/ci/setup_env.sh b/ci/setup_env.sh
index c36422884f2ec..e6bd9950331ca 100755
--- a/ci/setup_env.sh
+++ b/ci/setup_env.sh
@@ -12,41 +12,30 @@ if [[ "$(uname)" == "Linux" && -n "$LC_ALL" ]]; then
     echo
 fi
 
-MINICONDA_DIR="$HOME/miniconda3"
-
-
-if [ -d "$MINICONDA_DIR" ]; then
-    echo
-    echo "rm -rf "$MINICONDA_DIR""
-    rm -rf "$MINICONDA_DIR"
-fi
 
 echo "Install Miniconda"
-UNAME_OS=$(uname)
-if [[ "$UNAME_OS" == 'Linux' ]]; then
+DEFAULT_CONDA_URL="https://repo.continuum.io/miniconda/Miniconda3-latest"
+if [[ "$(uname -m)" == 'aarch64' ]]; then
+    CONDA_URL="https://github.com/conda-forge/miniforge/releases/download/4.10.1-4/Miniforge3-4.10.1-4-Linux-aarch64.sh"
+elif [[ "$(uname)" == 'Linux' ]]; then
     if [[ "$BITS32" == "yes" ]]; then
-        CONDA_OS="Linux-x86"
+        CONDA_URL="$DEFAULT_CONDA_URL-Linux-x86.sh"
     else
-        CONDA_OS="Linux-x86_64"
+        CONDA_URL="$DEFAULT_CONDA_URL-Linux-x86_64.sh"
     fi
-elif [[ "$UNAME_OS" == 'Darwin' ]]; then
-    CONDA_OS="MacOSX-x86_64"
+elif [[ "$(uname)" == 'Darwin' ]]; then
+    CONDA_URL="$DEFAULT_CONDA_URL-MacOSX-x86_64.sh"
 else
-  echo "OS $UNAME_OS not supported"
+  echo "OS $(uname) not supported"
   exit 1
 fi
-
-if [ "${TRAVIS_CPU_ARCH}" == "arm64" ]; then
-  CONDA_URL="https://github.com/conda-forge/miniforge/releases/download/4.8.5-1/Miniforge3-4.8.5-1-Linux-aarch64.sh"
-else
-  CONDA_URL="https://repo.continuum.io/miniconda/Miniconda3-latest-$CONDA_OS.sh"
-fi
+echo "Downloading $CONDA_URL"
 wget -q $CONDA_URL -O miniconda.sh
 chmod +x miniconda.sh
 
-# Installation path is required for ARM64 platform as miniforge script installs in path $HOME/miniforge3.
+MINICONDA_DIR="$HOME/miniconda3"
+rm -rf $MINICONDA_DIR
 ./miniconda.sh -b -p $MINICONDA_DIR
-
 export PATH=$MINICONDA_DIR/bin:$PATH
 
 echo
diff --git a/doc/_templates/sidebar-nav-bs.html b/doc/_templates/sidebar-nav-bs.html
new file mode 100644
index 0000000000000..7e0043e771e72
--- /dev/null
+++ b/doc/_templates/sidebar-nav-bs.html
@@ -0,0 +1,9 @@
+<nav class="bd-links" id="bd-docs-nav" aria-label="Main navigation">
+  <div class="bd-toc-item active">
+    {% if pagename.startswith("reference") %}
+    {{ generate_nav_html("sidebar", maxdepth=4, collapse=True, includehidden=True, titles_only=True) }}
+    {% else %}
+    {{ generate_nav_html("sidebar", maxdepth=4, collapse=False, includehidden=True, titles_only=True) }}
+    {% endif %}
+  </div>
+</nav>
diff --git a/doc/source/whatsnew/index.rst b/doc/source/whatsnew/index.rst
index 8739694c20e33..e546c8c8b80e3 100644
--- a/doc/source/whatsnew/index.rst
+++ b/doc/source/whatsnew/index.rst
@@ -16,6 +16,7 @@ Version 1.2
 .. toctree::
    :maxdepth: 2
 
+   v1.2.5
    v1.2.4
    v1.2.3
    v1.2.2
diff --git a/doc/source/whatsnew/v1.2.4.rst b/doc/source/whatsnew/v1.2.4.rst
index dd74091b64014..433ee37508e66 100644
--- a/doc/source/whatsnew/v1.2.4.rst
+++ b/doc/source/whatsnew/v1.2.4.rst
@@ -30,4 +30,4 @@ Fixed regressions
 Contributors
 ~~~~~~~~~~~~
 
-.. contributors:: v1.2.3..v1.2.4|HEAD
+.. contributors:: v1.2.3..v1.2.4
diff --git a/doc/source/whatsnew/v1.2.5.rst b/doc/source/whatsnew/v1.2.5.rst
new file mode 100644
index 0000000000000..d3ceb2b919b5d
--- /dev/null
+++ b/doc/source/whatsnew/v1.2.5.rst
@@ -0,0 +1,31 @@
+.. _whatsnew_125:
+
+What's new in 1.2.5 (June 22, 2021)
+-----------------------------------
+
+These are the changes in pandas 1.2.5. See :ref:`release` for a full changelog
+including other versions of pandas.
+
+{{ header }}
+
+.. ---------------------------------------------------------------------------
+
+.. _whatsnew_125.regressions:
+
+Fixed regressions
+~~~~~~~~~~~~~~~~~
+- Fixed regression in :func:`concat` between two :class:`DataFrame` where one has an :class:`Index` that is all-None and the other is :class:`DatetimeIndex` incorrectly raising (:issue:`40841`)
+- Fixed regression in :meth:`DataFrame.sum` and :meth:`DataFrame.prod` when ``min_count`` and ``numeric_only`` are both given (:issue:`41074`)
+- Fixed regression in :func:`read_csv` when using ``memory_map=True`` with an non-UTF8 encoding (:issue:`40986`)
+- Fixed regression in :meth:`DataFrame.replace` and :meth:`Series.replace` when the values to replace is a NumPy float array (:issue:`40371`)
+- Fixed regression in :func:`ExcelFile` when a corrupt file is opened but not closed (:issue:`41778`)
+- Fixed regression in :meth:`DataFrame.astype` with ``dtype=str`` failing to convert ``NaN`` in categorical columns (:issue:`41797`)
+
+.. ---------------------------------------------------------------------------
+
+.. _whatsnew_125.contributors:
+
+Contributors
+~~~~~~~~~~~~
+
+.. contributors:: v1.2.4..v1.2.5|HEAD
diff --git a/environment.yml b/environment.yml
index a369f656cb575..ec3c31a15ee02 100644
--- a/environment.yml
+++ b/environment.yml
@@ -4,7 +4,7 @@ channels:
 dependencies:
   # required
   - numpy>=1.16.5
-  - python=3
+  - python=3.8
   - python-dateutil>=2.7.3
   - pytz
 
@@ -20,7 +20,7 @@ dependencies:
   # code checks
   - black=20.8b1
   - cpplint
-  - flake8
+  - flake8=3.9.2
   - flake8-comprehensions>=3.1.0  # used by flake8, linting of unnecessary comprehensions
   - isort>=5.2.1  # check that imports are in the right order
   - mypy=0.782
@@ -77,7 +77,7 @@ dependencies:
   - bottleneck>=1.2.1
   - ipykernel
   - ipython>=7.11.1
-  - jinja2  # pandas.Styler
+  - jinja2<3.0.0  # pandas.Styler
   - matplotlib>=2.2.2  # pandas.plotting, Series.plot, DataFrame.plot
   - numexpr>=2.6.8
   - scipy>=1.2
@@ -97,14 +97,14 @@ dependencies:
   - xlwt
   - odfpy
 
-  - fastparquet>=0.3.2  # pandas.read_parquet, DataFrame.to_parquet
+  - fastparquet>=0.3.2, <=0.5.0  # pandas.read_parquet, DataFrame.to_parquet
   - pyarrow>=0.15.0  # pandas.read_parquet, DataFrame.to_parquet, pandas.read_feather, DataFrame.to_feather
   - python-snappy  # required by pyarrow
 
   - pyqt>=5.9.2  # pandas.read_clipboard
   - pytables>=3.5.1  # pandas.read_hdf, DataFrame.to_hdf
   - s3fs>=0.4.0  # file IO when using 's3://...' path
-  - fsspec>=0.7.4  # for generic remote file operations
+  - fsspec>=0.7.4, <2021.6.0  # for generic remote file operations
   - gcsfs>=0.6.0  # file IO when using 'gcs://...' path
   - sqlalchemy  # pandas.read_sql, DataFrame.to_sql
   - xarray  # DataFrame.to_xarray
diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 2ac9b9e2c875c..9aa261fd745d5 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -77,6 +77,18 @@ def is_platform_mac() -> bool:
     return sys.platform == "darwin"
 
 
+def is_platform_arm() -> bool:
+    """
+    Checking if he running platform use ARM architecture.
+
+    Returns
+    -------
+    bool
+        True if the running platform uses ARM architecture.
+    """
+    return platform.machine() in ("arm64", "aarch64")
+
+
 def import_lzma():
     """
     Importing the `lzma` module.
diff --git a/pandas/core/arrays/categorical.py b/pandas/core/arrays/categorical.py
index d5819697066ef..8b683d32f7b45 100644
--- a/pandas/core/arrays/categorical.py
+++ b/pandas/core/arrays/categorical.py
@@ -9,7 +9,7 @@
 
 from pandas._config import get_option
 
-from pandas._libs import NaT, algos as libalgos, hashtable as htable
+from pandas._libs import NaT, algos as libalgos, hashtable as htable, lib
 from pandas._libs.lib import no_default
 from pandas._typing import ArrayLike, Dtype, Ordered, Scalar
 from pandas.compat.numpy import function as nv
@@ -429,6 +429,7 @@ def astype(self, dtype: Dtype, copy: bool = True) -> ArrayLike:
             try:
                 new_cats = np.asarray(self.categories)
                 new_cats = new_cats.astype(dtype=dtype, copy=copy)
+                fill_value = lib.item_from_zerodim(np.array(np.nan).astype(dtype))
             except (
                 TypeError,  # downstream error msg for CategoricalIndex is misleading
                 ValueError,
@@ -436,7 +437,11 @@ def astype(self, dtype: Dtype, copy: bool = True) -> ArrayLike:
                 msg = f"Cannot cast {self.categories.dtype} dtype to {dtype}"
                 raise ValueError(msg)
 
-            result = take_1d(new_cats, libalgos.ensure_platform_int(self._codes))
+            result = take_1d(
+                new_cats,
+                libalgos.ensure_platform_int(self._codes),
+                fill_value=fill_value,
+            )
 
         return result
 
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 4c156d7470364..92892ac0f26e0 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -8786,7 +8786,6 @@ def _reduce(
         **kwds,
     ):
 
-        min_count = kwds.get("min_count", 0)
         assert filter_type is None or filter_type == "bool", filter_type
         out_dtype = "bool" if filter_type == "bool" else None
 
@@ -8831,7 +8830,7 @@ def _get_data() -> DataFrame:
                 data = self._get_bool_data()
             return data
 
-        if (numeric_only is not None or axis == 0) and min_count == 0:
+        if numeric_only is not None or axis == 0:
             # For numeric_only non-None and axis non-None, we know
             #  which blocks to use and no try/except is needed.
             #  For numeric_only=None only the case with axis==0 and no object
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 11d191597d61e..25860d6a4ecb3 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -2742,7 +2742,8 @@ def _union(self, other, sort):
                 # worth making this faster? a very unusual case
                 value_set = set(lvals)
                 result.extend([x for x in rvals if x not in value_set])
-                result = Index(result)._values  # do type inference here
+                # If objects are unorderable, we must have object dtype.
+                return np.array(result, dtype=object)
         else:
             # find indexes of things in "other" that are not in "self"
             if self.is_unique:
diff --git a/pandas/core/internals/blocks.py b/pandas/core/internals/blocks.py
index b6bca855a9f05..a38b7a19dc80a 100644
--- a/pandas/core/internals/blocks.py
+++ b/pandas/core/internals/blocks.py
@@ -391,7 +391,7 @@ def reduce(self, func, ignore_failures: bool = False) -> List["Block"]:
                 return []
             raise
 
-        if np.ndim(result) == 0:
+        if self.values.ndim == 1:
             # TODO(EA2D): special case not needed with 2D EAs
             res_values = np.array([[result]])
         else:
@@ -860,6 +860,15 @@ def _replace_list(
         """
         See BlockManager._replace_list docstring.
         """
+
+        # https://github.com/pandas-dev/pandas/issues/40371
+        # the following pairs check code caused a regression so we catch that case here
+        # until the issue is fixed properly in can_hold_element
+
+        # error: "Iterable[Any]" has no attribute "tolist"
+        if hasattr(src_list, "tolist"):
+            src_list = src_list.tolist()  # type: ignore[attr-defined]
+
         # Exclude anything that we know we won't contain
         pairs = [
             (x, y) for x, y in zip(src_list, dest_list) if self._can_hold_element(x)
diff --git a/pandas/core/nanops.py b/pandas/core/nanops.py
index edc1b1e96509e..d42497c3a8322 100644
--- a/pandas/core/nanops.py
+++ b/pandas/core/nanops.py
@@ -1377,8 +1377,15 @@ def _maybe_null_out(
     Dtype
         The product of all elements on a given axis. ( NaNs are treated as 1)
     """
-    if mask is not None and axis is not None and getattr(result, "ndim", False):
-        null_mask = (mask.shape[axis] - mask.sum(axis) - min_count) < 0
+    if axis is not None and isinstance(result, np.ndarray):
+        if mask is not None:
+            null_mask = (mask.shape[axis] - mask.sum(axis) - min_count) < 0
+        else:
+            # we have no nulls, kept mask=None in _maybe_get_mask
+            below_count = shape[axis] - min_count < 0
+            new_shape = shape[:axis] + shape[axis + 1 :]
+            null_mask = np.broadcast_to(below_count, new_shape)
+
         if np.any(null_mask):
             if is_numeric_dtype(result):
                 if np.iscomplexobj(result):
diff --git a/pandas/io/common.py b/pandas/io/common.py
index be353fefdd1ef..e6b6471294ac7 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -568,7 +568,12 @@ def get_handle(
 
     # memory mapping needs to be the first step
     handle, memory_map, handles = _maybe_memory_map(
-        handle, memory_map, ioargs.encoding, ioargs.mode, errors
+        handle,
+        memory_map,
+        ioargs.encoding,
+        ioargs.mode,
+        errors,
+        ioargs.compression["method"] not in _compression_to_extension,
     )
 
     is_path = isinstance(handle, str)
@@ -759,7 +764,18 @@ class _MMapWrapper(abc.Iterator):
 
     """
 
-    def __init__(self, f: IO):
+    def __init__(
+        self,
+        f: IO,
+        encoding: str = "utf-8",
+        errors: str = "strict",
+        decode: bool = True,
+    ):
+        self.encoding = encoding
+        self.errors = errors
+        self.decoder = codecs.getincrementaldecoder(encoding)(errors=errors)
+        self.decode = decode
+
         self.attributes = {}
         for attribute in ("seekable", "readable", "writeable"):
             if not hasattr(f, attribute):
@@ -775,19 +791,31 @@ def __getattr__(self, name: str):
     def __iter__(self) -> "_MMapWrapper":
         return self
 
+    def read(self, size: int = -1) -> Union[str, bytes]:
+        # CSV c-engine uses read instead of iterating
+        content: bytes = self.mmap.read(size)
+        if self.decode:
+            errors = self.errors if self.errors is not None else "strict"
+            # memory mapping is applied before compression. Encoding should
+            # be applied to the de-compressed data.
+            return content.decode(self.encoding, errors=errors)
+        return content
+
     def __next__(self) -> str:
         newbytes = self.mmap.readline()
 
         # readline returns bytes, not str, but Python's CSV reader
         # expects str, so convert the output to str before continuing
-        newline = newbytes.decode("utf-8")
+        newline = self.decoder.decode(newbytes)
 
         # mmap doesn't raise if reading past the allocated
         # data but instead returns an empty string, so raise
         # if that is returned
         if newline == "":
             raise StopIteration
-        return newline
+
+        # IncrementalDecoder seems to push newline to the next line
+        return newline.lstrip("\n")
 
 
 def _maybe_memory_map(
@@ -796,6 +824,7 @@ def _maybe_memory_map(
     encoding: str,
     mode: str,
     errors: Optional[str],
+    decode: bool,
 ) -> Tuple[FileOrBuffer, bool, List[Buffer]]:
     """Try to memory map file/buffer."""
     handles: List[Buffer] = []
@@ -814,7 +843,10 @@ def _maybe_memory_map(
         handles.append(handle)
 
     try:
-        wrapped = cast(mmap.mmap, _MMapWrapper(handle))  # type: ignore[arg-type]
+        wrapped = cast(
+            mmap.mmap,
+            _MMapWrapper(handle, encoding, errors, decode),  # type: ignore[arg-type]
+        )
         handle.close()
         handles.remove(handle)
         handles.append(wrapped)
diff --git a/pandas/io/excel/_base.py b/pandas/io/excel/_base.py
index 850570fc743b7..11dee69651dad 100644
--- a/pandas/io/excel/_base.py
+++ b/pandas/io/excel/_base.py
@@ -388,7 +388,11 @@ def __init__(self, filepath_or_buffer, storage_options: StorageOptions = None):
         elif hasattr(self.handles.handle, "read"):
             # N.B. xlrd.Book has a read attribute too
             self.handles.handle.seek(0)
-            self.book = self.load_workbook(self.handles.handle)
+            try:
+                self.book = self.load_workbook(self.handles.handle)
+            except Exception:
+                self.close()
+                raise
         elif isinstance(self.handles.handle, bytes):
             self.book = self.load_workbook(BytesIO(self.handles.handle))
         else:
@@ -406,6 +410,11 @@ def load_workbook(self, filepath_or_buffer):
         pass
 
     def close(self):
+        if hasattr(self, "book") and hasattr(self.book, "close"):
+            # pyxlsb: opens a TemporaryFile
+            # openpyxl: https://stackoverflow.com/questions/31416842/
+            #     openpyxl-does-not-close-excel-workbook-in-read-only-mode
+            self.book.close()
         self.handles.close()
 
     @property
diff --git a/pandas/io/excel/_openpyxl.py b/pandas/io/excel/_openpyxl.py
index be1587dbc010c..cac6d8d1b8113 100644
--- a/pandas/io/excel/_openpyxl.py
+++ b/pandas/io/excel/_openpyxl.py
@@ -487,12 +487,6 @@ def load_workbook(self, filepath_or_buffer: FilePathOrBuffer):
             filepath_or_buffer, read_only=True, data_only=True, keep_links=False
         )
 
-    def close(self):
-        # https://stackoverflow.com/questions/31416842/
-        #  openpyxl-does-not-close-excel-workbook-in-read-only-mode
-        self.book.close()
-        super().close()
-
     @property
     def sheet_names(self) -> List[str]:
         return self.book.sheetnames
diff --git a/pandas/io/parsers.py b/pandas/io/parsers.py
index 8ad86fd0a0dce..bbff9dfe1ddd0 100644
--- a/pandas/io/parsers.py
+++ b/pandas/io/parsers.py
@@ -1868,31 +1868,6 @@ def __init__(self, src: FilePathOrBuffer, **kwds):
         assert self.handles is not None
         for key in ("storage_options", "encoding", "memory_map", "compression"):
             kwds.pop(key, None)
-        if self.handles.is_mmap and hasattr(self.handles.handle, "mmap"):
-            # pandas\io\parsers.py:1861: error: Item "IO[Any]" of
-            # "Union[IO[Any], RawIOBase, BufferedIOBase, TextIOBase,
-            # TextIOWrapper, mmap]" has no attribute "mmap"  [union-attr]
-
-            # pandas\io\parsers.py:1861: error: Item "RawIOBase" of
-            # "Union[IO[Any], RawIOBase, BufferedIOBase, TextIOBase,
-            # TextIOWrapper, mmap]" has no attribute "mmap"  [union-attr]
-
-            # pandas\io\parsers.py:1861: error: Item "BufferedIOBase" of
-            # "Union[IO[Any], RawIOBase, BufferedIOBase, TextIOBase,
-            # TextIOWrapper, mmap]" has no attribute "mmap"  [union-attr]
-
-            # pandas\io\parsers.py:1861: error: Item "TextIOBase" of
-            # "Union[IO[Any], RawIOBase, BufferedIOBase, TextIOBase,
-            # TextIOWrapper, mmap]" has no attribute "mmap"  [union-attr]
-
-            # pandas\io\parsers.py:1861: error: Item "TextIOWrapper" of
-            # "Union[IO[Any], RawIOBase, BufferedIOBase, TextIOBase,
-            # TextIOWrapper, mmap]" has no attribute "mmap"  [union-attr]
-
-            # pandas\io\parsers.py:1861: error: Item "mmap" of "Union[IO[Any],
-            # RawIOBase, BufferedIOBase, TextIOBase, TextIOWrapper, mmap]" has
-            # no attribute "mmap"  [union-attr]
-            self.handles.handle = self.handles.handle.mmap  # type: ignore[union-attr]
 
         try:
             self._reader = parsers.TextReader(self.handles.handle, **kwds)
diff --git a/pandas/tests/arithmetic/common.py b/pandas/tests/arithmetic/common.py
index e26bb513838a5..d42da39ec8ff0 100644
--- a/pandas/tests/arithmetic/common.py
+++ b/pandas/tests/arithmetic/common.py
@@ -83,6 +83,7 @@ def xbox2(x):
             "Invalid comparison between",
             "Cannot compare type",
             "not supported between",
+            "could not be promoted",
             "invalid type promotion",
             (
                 # GH#36706 npdev 1.20.0 2020-09-28
diff --git a/pandas/tests/arithmetic/test_interval.py b/pandas/tests/arithmetic/test_interval.py
index 6dc3b3b13dd0c..4473d86fa04a1 100644
--- a/pandas/tests/arithmetic/test_interval.py
+++ b/pandas/tests/arithmetic/test_interval.py
@@ -235,7 +235,7 @@ def test_compare_list_like_nan(self, op, array, nulls_fixture, request):
             Categorical(list("abab")),
             Categorical(date_range("2017-01-01", periods=4)),
             pd.array(list("abcd")),
-            pd.array(["foo", 3.14, None, object()]),
+            pd.array(["foo", 3.14, None, object()], dtype=object),
         ],
         ids=lambda x: str(x.dtype),
     )
diff --git a/pandas/tests/arrays/boolean/test_arithmetic.py b/pandas/tests/arrays/boolean/test_arithmetic.py
index 9b854a81f2def..01de64568a011 100644
--- a/pandas/tests/arrays/boolean/test_arithmetic.py
+++ b/pandas/tests/arrays/boolean/test_arithmetic.py
@@ -66,10 +66,7 @@ def test_div(left_array, right_array):
 @pytest.mark.parametrize(
     "opname",
     [
-        pytest.param(
-            "floordiv",
-            marks=pytest.mark.xfail(reason="NumpyDev GH#40874", strict=False),
-        ),
+        "floordiv",
         "mod",
         pytest.param(
             "pow", marks=pytest.mark.xfail(reason="TODO follow int8 behaviour? GH34686")
diff --git a/pandas/tests/arrays/masked/test_arithmetic.py b/pandas/tests/arrays/masked/test_arithmetic.py
index 34686f6052131..148b7092abb56 100644
--- a/pandas/tests/arrays/masked/test_arithmetic.py
+++ b/pandas/tests/arrays/masked/test_arithmetic.py
@@ -3,8 +3,6 @@
 import numpy as np
 import pytest
 
-from pandas.compat.numpy import is_numpy_dev
-
 import pandas as pd
 import pandas._testing as tm
 from pandas.core.arrays import ExtensionArray
@@ -51,8 +49,6 @@ def test_array_scalar_like_equivalence(data, all_arithmetic_operators):
 def test_array_NA(data, all_arithmetic_operators):
     if "truediv" in all_arithmetic_operators:
         pytest.skip("division with pd.NA raises")
-    if "floordiv" in all_arithmetic_operators and is_numpy_dev:
-        pytest.skip("NumpyDev behavior GH#40874")
     data, _ = data
     op = tm.get_op_from_name(all_arithmetic_operators)
     check_skip(data, all_arithmetic_operators)
diff --git a/pandas/tests/extension/test_boolean.py b/pandas/tests/extension/test_boolean.py
index d15c822f22c14..86a0bc9213256 100644
--- a/pandas/tests/extension/test_boolean.py
+++ b/pandas/tests/extension/test_boolean.py
@@ -16,8 +16,6 @@
 import numpy as np
 import pytest
 
-from pandas.compat.numpy import is_numpy_dev
-
 import pandas as pd
 import pandas._testing as tm
 from pandas.core.arrays.boolean import BooleanDtype
@@ -141,21 +139,6 @@ def _check_op(self, s, op, other, op_name, exc=NotImplementedError):
             with pytest.raises(exc):
                 op(s, other)
 
-    def test_arith_series_with_scalar(self, data, all_arithmetic_operators):
-        if "floordiv" in all_arithmetic_operators and is_numpy_dev:
-            pytest.skip("NumpyDev behavior GH#40874")
-        super().test_arith_series_with_scalar(data, all_arithmetic_operators)
-
-    def test_arith_series_with_array(self, data, all_arithmetic_operators):
-        if "floordiv" in all_arithmetic_operators and is_numpy_dev:
-            pytest.skip("NumpyDev behavior GH#40874")
-        super().test_arith_series_with_scalar(data, all_arithmetic_operators)
-
-    def test_divmod_series_array(self, data, data_for_twos):
-        if is_numpy_dev:
-            pytest.skip("NumpyDev behavior GH#40874")
-        super().test_divmod_series_array(data, data_for_twos)
-
     def _check_divmod_op(self, s, op, other, exc=None):
         # override to not raise an error
         super()._check_divmod_op(s, op, other, None)
diff --git a/pandas/tests/frame/methods/test_astype.py b/pandas/tests/frame/methods/test_astype.py
index 5264d4b432d34..0d160966521d3 100644
--- a/pandas/tests/frame/methods/test_astype.py
+++ b/pandas/tests/frame/methods/test_astype.py
@@ -616,3 +616,11 @@ def test_astype_bytes(self):
         # GH#39474
         result = DataFrame(["foo", "bar", "baz"]).astype(bytes)
         assert result.dtypes[0] == np.dtype("S3")
+
+    def test_astype_categorical_to_string_missing(self):
+        # https://github.com/pandas-dev/pandas/issues/41797
+        df = DataFrame(["a", "b", np.nan])
+        expected = df.astype(str)
+        cat = df.astype("category")
+        result = cat.astype(str)
+        tm.assert_frame_equal(result, expected)
diff --git a/pandas/tests/frame/methods/test_replace.py b/pandas/tests/frame/methods/test_replace.py
index c4f2e09911b34..0f85af6b26aa3 100644
--- a/pandas/tests/frame/methods/test_replace.py
+++ b/pandas/tests/frame/methods/test_replace.py
@@ -1665,3 +1665,22 @@ def test_replace_bytes(self, frame_or_series):
         expected = obj.copy()
         obj = obj.replace({None: np.nan})
         tm.assert_equal(obj, expected)
+
+    @pytest.mark.parametrize(
+        "data, to_replace, value, expected",
+        [
+            ([1], [1.0], [0], [0]),
+            ([1], [1], [0], [0]),
+            ([1.0], [1.0], [0], [0.0]),
+            ([1.0], [1], [0], [0.0]),
+        ],
+    )
+    @pytest.mark.parametrize("box", [list, tuple, np.array])
+    def test_replace_list_with_mixed_type(
+        self, data, to_replace, value, expected, box, frame_or_series
+    ):
+        # GH#40371
+        obj = frame_or_series(data)
+        expected = frame_or_series(expected)
+        result = obj.replace(box(to_replace), value)
+        tm.assert_equal(result, expected)
diff --git a/pandas/tests/frame/test_arithmetic.py b/pandas/tests/frame/test_arithmetic.py
index e5ec3c5641bd2..51420859dc1bd 100644
--- a/pandas/tests/frame/test_arithmetic.py
+++ b/pandas/tests/frame/test_arithmetic.py
@@ -79,6 +79,7 @@ def check(df, df2):
                 msgs = [
                     r"Invalid comparison between dtype=datetime64\[ns\] and ndarray",
                     "invalid type promotion",
+                    "could not be promoted",
                     (
                         # npdev 1.20.0
                         r"The DTypes <class 'numpy.dtype\[.*\]'> and "
diff --git a/pandas/tests/frame/test_reductions.py b/pandas/tests/frame/test_reductions.py
index cb481613eb97f..b6eccc6999dec 100644
--- a/pandas/tests/frame/test_reductions.py
+++ b/pandas/tests/frame/test_reductions.py
@@ -1,5 +1,6 @@
 from datetime import timedelta
 from decimal import Decimal
+import re
 
 from dateutil.tz import tzlocal
 import numpy as np
@@ -783,34 +784,35 @@ def test_sum_corner(self):
         assert len(axis1) == 0
 
     @pytest.mark.parametrize("method, unit", [("sum", 0), ("prod", 1)])
-    def test_sum_prod_nanops(self, method, unit):
+    @pytest.mark.parametrize("numeric_only", [None, True, False])
+    def test_sum_prod_nanops(self, method, unit, numeric_only):
         idx = ["a", "b", "c"]
         df = DataFrame({"a": [unit, unit], "b": [unit, np.nan], "c": [np.nan, np.nan]})
         # The default
-        result = getattr(df, method)
+        result = getattr(df, method)(numeric_only=numeric_only)
         expected = Series([unit, unit, unit], index=idx, dtype="float64")
 
         # min_count=1
-        result = getattr(df, method)(min_count=1)
+        result = getattr(df, method)(numeric_only=numeric_only, min_count=1)
         expected = Series([unit, unit, np.nan], index=idx)
         tm.assert_series_equal(result, expected)
 
         # min_count=0
-        result = getattr(df, method)(min_count=0)
+        result = getattr(df, method)(numeric_only=numeric_only, min_count=0)
         expected = Series([unit, unit, unit], index=idx, dtype="float64")
         tm.assert_series_equal(result, expected)
 
-        result = getattr(df.iloc[1:], method)(min_count=1)
+        result = getattr(df.iloc[1:], method)(numeric_only=numeric_only, min_count=1)
         expected = Series([unit, np.nan, np.nan], index=idx)
         tm.assert_series_equal(result, expected)
 
         # min_count > 1
         df = DataFrame({"A": [unit] * 10, "B": [unit] * 5 + [np.nan] * 5})
-        result = getattr(df, method)(min_count=5)
+        result = getattr(df, method)(numeric_only=numeric_only, min_count=5)
         expected = Series(result, index=["A", "B"])
         tm.assert_series_equal(result, expected)
 
-        result = getattr(df, method)(min_count=6)
+        result = getattr(df, method)(numeric_only=numeric_only, min_count=6)
         expected = Series(result, index=["A", "B"])
         tm.assert_series_equal(result, expected)
 
@@ -1491,3 +1493,16 @@ def test_minmax_extensionarray(method, numeric_only):
         [getattr(int64_info, method)], index=Index(["Int64"], dtype="object")
     )
     tm.assert_series_equal(result, expected)
+
+
+def test_prod_sum_min_count_mixed_object():
+    # https://github.com/pandas-dev/pandas/issues/41074
+    df = DataFrame([1, "a", True])
+
+    result = df.prod(axis=0, min_count=1, numeric_only=False)
+    expected = Series(["a"])
+    tm.assert_series_equal(result, expected)
+
+    msg = re.escape("unsupported operand type(s) for +: 'int' and 'str'")
+    with pytest.raises(TypeError, match=msg):
+        df.sum(axis=0, min_count=1, numeric_only=False)
diff --git a/pandas/tests/io/excel/test_readers.py b/pandas/tests/io/excel/test_readers.py
index bd3bfa207c4b0..e4006d9068f2a 100644
--- a/pandas/tests/io/excel/test_readers.py
+++ b/pandas/tests/io/excel/test_readers.py
@@ -1,6 +1,7 @@
 from datetime import datetime, time
 from functools import partial
 import os
+from pathlib import Path
 from urllib.error import URLError
 from zipfile import BadZipFile
 
@@ -1273,3 +1274,21 @@ def test_read_datetime_multiindex(self, engine, read_ext):
         expected = DataFrame([], columns=expected_column_index)
 
         tm.assert_frame_equal(expected, actual)
+
+    def test_corrupt_files_closed(self, request, engine, read_ext):
+        # GH41778
+        errors = (BadZipFile, ValueError)
+        if engine is None:
+            pytest.skip()
+        elif engine == "xlrd":
+            import xlrd
+
+            errors = (BadZipFile, ValueError, xlrd.biffh.XLRDError)
+
+        with tm.ensure_clean(f"corrupt{read_ext}") as file:
+            Path(file).write_text("corrupt")
+            with tm.assert_produces_warning(False):
+                try:
+                    pd.ExcelFile(file, engine=engine)
+                except errors:
+                    pass
diff --git a/pandas/tests/io/parser/test_encoding.py b/pandas/tests/io/parser/test_encoding.py
index e74265da3e966..41e1964086dce 100644
--- a/pandas/tests/io/parser/test_encoding.py
+++ b/pandas/tests/io/parser/test_encoding.py
@@ -217,3 +217,20 @@ def test_parse_encoded_special_characters(encoding):
 
     expected = DataFrame(data=[["：foo", 0], ["bar", 1], ["baz", 2]], columns=["a", "b"])
     tm.assert_frame_equal(result, expected)
+
+
+@pytest.mark.parametrize("encoding", ["utf-8", None, "utf-16", "cp1255", "latin-1"])
+def test_encoding_memory_map(all_parsers, encoding):
+    # GH40986
+    parser = all_parsers
+    expected = DataFrame(
+        {
+            "name": ["Raphael", "Donatello", "Miguel Angel", "Leonardo"],
+            "mask": ["red", "purple", "orange", "blue"],
+            "weapon": ["sai", "bo staff", "nunchunk", "katana"],
+        }
+    )
+    with tm.ensure_clean() as file:
+        expected.to_csv(file, index=False, encoding=encoding)
+        df = parser.read_csv(file, encoding=encoding, memory_map=True)
+    tm.assert_frame_equal(df, expected)
diff --git a/pandas/tests/reshape/concat/test_concat.py b/pandas/tests/reshape/concat/test_concat.py
index cd58df4fc5da6..3b11a5dbda41c 100644
--- a/pandas/tests/reshape/concat/test_concat.py
+++ b/pandas/tests/reshape/concat/test_concat.py
@@ -572,3 +572,23 @@ def test_concat_repeated_keys(keys, integrity):
     tuples = list(zip(keys, ["a", "b", "c"]))
     expected = Series([1, 2, 3], index=MultiIndex.from_tuples(tuples))
     tm.assert_series_equal(result, expected)
+
+
+def test_concat_null_object_with_dti():
+    # GH#40841
+    dti = pd.DatetimeIndex(
+        ["2021-04-08 21:21:14+00:00"], dtype="datetime64[ns, UTC]", name="Time (UTC)"
+    )
+    right = DataFrame(data={"C": [0.5274]}, index=dti)
+
+    idx = Index([None], dtype="object", name="Maybe Time (UTC)")
+    left = DataFrame(data={"A": [None], "B": [np.nan]}, index=idx)
+
+    result = concat([left, right], axis="columns")
+
+    exp_index = Index([None, dti[0]], dtype=object)
+    expected = DataFrame(
+        {"A": [None, None], "B": [np.nan, np.nan], "C": [np.nan, 0.5274]},
+        index=exp_index,
+    )
+    tm.assert_frame_equal(result, expected)
diff --git a/pandas/tests/window/test_rolling.py b/pandas/tests/window/test_rolling.py
index e2cdf76d038ec..218d247a25380 100644
--- a/pandas/tests/window/test_rolling.py
+++ b/pandas/tests/window/test_rolling.py
@@ -3,6 +3,7 @@
 import numpy as np
 import pytest
 
+from pandas.compat import is_platform_arm
 from pandas.errors import UnsupportedFunctionCall
 
 from pandas import (
@@ -891,6 +892,7 @@ def test_rolling_sem(frame_or_series):
     tm.assert_series_equal(result, expected)
 
 
+@pytest.mark.xfail(is_platform_arm(), reason="GH 41740")
 @pytest.mark.parametrize(
     ("func", "third_value", "values"),
     [
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 595b2ee537e63..78aca0913b006 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -8,7 +8,7 @@ asv
 cython>=0.29.21
 black==20.8b1
 cpplint
-flake8
+flake8==3.9.2
 flake8-comprehensions>=3.1.0
 isort>=5.2.1
 mypy==0.782
@@ -49,7 +49,7 @@ blosc
 bottleneck>=1.2.1
 ipykernel
 ipython>=7.11.1
-jinja2
+jinja2<3.0.0
 matplotlib>=2.2.2
 numexpr>=2.6.8
 scipy>=1.2
@@ -62,13 +62,13 @@ xlrd
 xlsxwriter
 xlwt
 odfpy
-fastparquet>=0.3.2
+fastparquet>=0.3.2, <=0.5.0
 pyarrow>=0.15.0
 python-snappy
 pyqt5>=5.9.2
 tables>=3.5.1
 s3fs>=0.4.0
-fsspec>=0.7.4
+fsspec>=0.7.4, <2021.6.0
 gcsfs>=0.6.0
 sqlalchemy
 xarray
diff --git a/scripts/tests/test_validate_docstrings.py b/scripts/tests/test_validate_docstrings.py
index 7e4c68ddc183b..cbf3e84044d53 100644
--- a/scripts/tests/test_validate_docstrings.py
+++ b/scripts/tests/test_validate_docstrings.py
@@ -165,7 +165,7 @@ def test_bad_class(self, capsys):
                 "indentation_is_not_a_multiple_of_four",
                 # with flake8 3.9.0, the message ends with four spaces,
                 #  whereas in earlier versions, it ended with "four"
-                ("flake8 error: E111 indentation is not a multiple of     ",),
+                ("flake8 error: E111 indentation is not a multiple of 4",),
             ),
             (
                 "BadDocstrings",