when a GC collection happens in another thread.

Original patch and report by Armin Rigo.

Improved the documentation and tests for make_archive().
Improved error handling when corresponding compress module is not available.
External zip executable is now used if the zlib module is not available.

of old-style classes.

system Python site-packages directory, to sys.path for macOS framework builds.
The coupling between the two Python instances often caused confusion and, as
of macOS 10.12, changes to the site-packages layout can cause pip component
installations to fail.  This change reverts the effects introduced in 2.7.0
by Issue #4865.  If you are using a package with both the Apple system Python
2.7 and a user-installed Python 2.7, you will need to ensure that copies of
the package are installed with both Python instances.

names.

Original patch by Andreas Stührk.

changed and supports reading read-only files.