> Another issue with the tests is that it has become terribly slow. It's taking about 45 minutes to complete 1 run of the test suite. A few days ago, it took only 10 - 15 minutes.

It took 49 minutes on my Windows 10 VM. Are you sure that you ran the test suite sequentially when it was slower?

I advice you run using -j0 option to run tests in parallel: it's much faster, and it's also more reliable.

== Tests result: FAILURE ==

384 tests OK.

1 test failed:
    test_distutils

41 tests skipped:
    test_curses test_dbm_gnu test_dbm_ndbm test_devpoll test_epoll
    test_fcntl test_fork1 test_gdb test_grp test_ioctl test_kqueue
    test_multiprocessing_fork test_multiprocessing_forkserver test_nis
    test_openpty test_ossaudiodev test_pipes test_poll test_posix
    test_pty test_pwd test_readline test_resource test_smtpnet
    test_socketserver test_spwd test_syslog test_threadsignals
    test_timeout test_tix test_tk test_ttk_guionly test_urllib2net
    test_urllibnet test_wait3 test_wait4 test_winsound test_xmlrpc_net
    test_xxlimited test_xxtestfuzz test_zipfile64

Total duration: 49 min 12 sec
Tests result: FAILURE