ISsue #14988: restore Python 2's behavior of raising ImportError when unable to load pyexpat, instead of a SystemError/RuntimeError

Based on a patch by Nick Coghlan.

Issue #15230: Attempt to make the OS X buildbots happy by resolving the tmp dir symlink in the test suite

The asserts were useless (and buggy).

select.poll before running.  works both ways (finally).  this should fix
the windows build.

platforms that don't have it.

to avoid failing due to the select() file descriptor limit.

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