Pex cannot resolve pants libraries for OSX

[tglstory]

ci.txt

In version 1.11.0rc0, we are getting

Failed to execute PEX file, missing macosx_10_13_x86_64-cp-27-cp27m compatible dependencies for:
                     future
                     pantsbuild.pants.contrib.python.checks.checker
                     six
                     pycodestyle
                     pyflakes

for pythonstyle task. I've attached a verbosity 9 log.

[jsirois]

This repro's cleanly in a minimal repo. Digging...

[jsirois]

Definitely no obvious workaround hacks here. There will need to be an rc1 with a fix.

Still digging on root cause.

[jsirois]

Alright. For wheel releases where winding up here where we though we were inside a pex:

pants/contrib/python/src/python/pants/contrib/python/checks/tasks/checkstyle/checkstyle.py

Lines 142 to 147 in a368267

	# The checker is already on sys.path, eg: embedded in pants.pex.
	working_set = WorkingSet(entries=sys.path)
	for dist in working_set.resolve([Requirement.parse(self._CHECKER_REQ)]):
	pex_builder.add_direct_requirements(dist.requires())
	pex_builder.add_distribution(dist)
	pex_builder.add_direct_requirements([self._CHECKER_REQ])

The result is a very strange pex being built that can never work. One of its .deps/ embedded entries is all of site-packages.