bpo-26789: Fix logging.FileHandler._open() at exit (GH-23053)

The logging.FileHandler class now keeps a reference to the builtin
open() function to be able to open or reopen the file during Python
finalization.

Fix errors like:

    Exception ignored in: (...)
    Traceback (most recent call last):
      (...)
      File ".../logging/__init__.py", line 1463, in error
      File ".../logging/__init__.py", line 1577, in _log
      File ".../logging/__init__.py", line 1587, in handle
      File ".../logging/__init__.py", line 1649, in callHandlers
      File ".../logging/__init__.py", line 948, in handle
      File ".../logging/__init__.py", line 1182, in emit
      File ".../logging/__init__.py", line 1171, in _open
    NameError: name 'open' is not defined

1 files changed, 4 insertions, 0 deletions

diff --git a/Misc/NEWS.d/next/Library/2020-10-31-01-16-49.bpo-26789.9BdNAt.rst b/Misc/NEWS.d/next/Library/2020-10-31-01-16-49.bpo-26789.9BdNAt.rst
new file mode 100644
index 0000000..d883240
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-10-31-01-16-49.bpo-26789.9BdNAt.rst
@@ -0,0 +1,4 @@
+The :class:`logging.FileHandler` class now keeps a reference to the builtin
+:func:`open` function to be able to open or reopen the file during Python
+finalization. Fix errors like: ``NameError: name 'open' is not defined``. Patch
+by Victor Stinner.