shutdown to call objects destructors. So "unclosed file" resource warnings are
now corretly emitted for daemon threads.

The SMTP server advertises four different authentication methods, and
the code will try CRAM-MD5 first, which will fail, but LOGIN succeeds.

Patch by Donald Stufft and Nick Coghlan

delaying the main thread so that it doesn't race ahead of the workers.

(issue #16685).

Merge with 3.3 for Issue #19544 and Issue #6286. Merge is untested. I was unable to test due to bab0cbf86835.

Issue #19544 and Issue #6286: Restore use of urllib over http allowing use of http_proxy for Distutils upload command, a feature accidentally lost in the rollback of distutils2.

Issue 19544 and Issue #7457: Restore the read_pkg_file method to distutils.dist.DistributionMetadata accidentally removed in the undo of distutils2.

Removed support for strings.