bpo-30121: Fix test_subprocess for Windows Debug builds (GH-5758)

Author: zware

Lib/test/test_subprocess.py

@@ -1179,7 +1179,7 @@ def test_nonexisting_with_pipes(self):
                 msvcrt.CrtSetReportFile(report_type, msvcrt.CRTDBG_FILE_STDERR)
 
             try:
-                subprocess.Popen([cmd],
+                subprocess.Popen(cmd,
                                  stdout=subprocess.PIPE,
                                  stderr=subprocess.PIPE)
             except OSError: