Close #15230: runpy.run_path now sets __package__ correctly. Also refactored the runpy tests to use a more systematic approach

Patch by Jeremy Kloth.

Issue #15338: skip test_UNC_path when the current user doesn't have enough permissions to access the path.

Issue #15300: Ensure the temporary test working directories are in the same parent folder when running tests in multiprocess mode from a Python build.
Patch by Chris Jerdonek.

execfile().

Patch contributed by Stephen Thorne.

Issue #15020: The program name used to search for Python's path is now "python3" under Unix, not "python".

Fix issue # 15033 - Return the proper exitcode for failure when modules are invoked using -m switch. Patch contributed by Jeff Knupp

the Ctrl-C signal handler on Windows

Patch by Serhiy Storchaka.

Patch by Jakub Wilk.

If messages were only added, a new file is no longer created and
renamed over the old file when flush() is called on an mbox, MMDF or
Babyl mailbox.