bpo-30121: Fix debug assert in subprocess on Windows (#1224)

* bpo-30121: Fix debug assert in subprocess on Windows

This is caused by closing HANDLEs using os.close which is for CRT file
descriptors and not for HANDLEs.

* bpo-30121: Suppress debug assertion in test_subprocess when ran directly

1 files changed, 7 insertions, 1 deletions

diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 99bca477ce..2805ec3fa3 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -727,7 +727,10 @@ class Popen(object):
                     to_close.append(self._devnull)
                 for fd in to_close:
                     try:
-                        os.close(fd)
+                        if _mswindows and isinstance(fd, Handle):
+                            fd.Close()
+                        else:
+                            os.close(fd)
                     except OSError:
                         pass
 
@@ -1007,6 +1010,9 @@ class Popen(object):
                     errwrite.Close()
                 if hasattr(self, '_devnull'):
                     os.close(self._devnull)
+                # Prevent a double close of these handles/fds from __init__
+                # on error.
+                self._closed_child_pipe_fds = True
 
             # Retain the process handle, but close the thread handle
             self._child_created = True