Issue28082, for 3.6.0b1, modified the re module to use enum.IntFlag. As described in Issue19325, on interpreter startup site.py imports sysconfig which, on OS X, imports _osx_support which imports, among other things, re. Now that re imports enum, a number of collections modules are also imported at startup on OS X which can have a negative performance impact. test_startup_imports of test_site was designed to catch situations like this ... and does. For 3.6.0b1, I'm going to skip the failing part of the test on OS X only. For 3.6.0b2, I'll plan to revive languishing Issue19325 to at least try to remove the usage of re and then re-enable the skipped test.

New changeset 9f0016055820 by Ned Deily in branch 'default': Issue #28095: Temporarily disable part of test_startup_imports on OS X. https://hg.python.org/cpython/rev/9f0016055820

 New changeset c22bd58d933efaec26d1f77f263b2845473b7e15 by Ned Deily in branch 'master': bpo-28095: Re-enable temporarily disabled part of test_startup_imports on macOS (#2927) https://github.com/python/cpython/commit/c22bd58d933efaec26d1f77f263b2845473b7e15 

The changes for bpo-29585 to speed up startup removed the import of _osx_support, and of re, from site.py so the disabled test does not fail in 3.7 and is now re-enabled. It's not appropriate to try to backport the startup speedup changes to 3.6, so the disabled portion of the test remains disabled on 3.6.x macOS.