Make it less likely that multiple processes fail to create directories, which can sometimes break tests or builds.
(The option came in Python >=3.5. At least, it seems to be intended to be race-free: https://bugs.python.org/issue21082 if the discussion applies to os.mkdir, too)
Make it less likely that multiple processes fail to create directories, which can sometimes break tests or builds.
(The option came in Python >=3.5. At least, it seems to be intended to be race-free: https://bugs.python.org/issue21082 if the discussion applies to os.mkdir, too)
Closes #259