Rework akin to test_threaded_import, so that this can run under regrtest. Also raise TestSkipped (intead of appearing to fail) if the import lock is held.
Rework akin to test_threaded_import, so that this can run under regrtest.
Also raise TestSkipped (intead of appearing to fail) if the import lock
is held.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator