fix up test case

Author: sweeneyde

Lib/test/test_mmap.py

@@ -302,12 +302,17 @@ def test_find_end(self):
     def test_find_does_not_access_beyond_buffer(self):
         try:
             flags = mmap.MAP_PRIVATE | mmap.MAP_ANONYMOUS
-        except AttributeError:
-            raise unittest.SkipTest("mmap flags unavailable")
+            PAGESIZE = mmap.PAGESIZE
+            PROT_NONE = 0
+            PROT_READ = mmap.PROT_READ
+        except AttributeError as e:
+            raise unittest.SkipTest("mmap flags unavailable") from e
         for i in range(0, 2049):
-            with mmap.mmap(0, 4096 * (i + 1), flags=flags, prot=0) as guard:
-                with mmap.mmap(0, 8388608 + 4096 * i, flags=flags, prot=mmap.PROT_READ) as fm:
-                    fm.find(b"fo")
+            with mmap.mmap(-1, PAGESIZE * (i + 1),
+                           flags=flags, prot=PROT_NONE) as guard:
+                with mmap.mmap(-1, PAGESIZE * (i + 2048),
+                               flags=flags, prot=PROT_READ) as fm:
+                    fm.find(b"fo", -2)
 
     def test_rfind(self):
         # test the new 'end' parameter works as expected