scm_unittest.py fails at import-time on Python 2

[Sam Sneddon [:gsnedders]]

This isn't run by default (because it's too slow), but as a result we don't even try to import the tests and this has led to us regressing our ability to run them.

Notably, ./Tools/Scripts/test-webkitpy-python2 --all currently fails:

Checking imports ...Failed to import webkitpy.common.checkout.scm.scm_unittest:
Failed to import webkitpy.common.checkout.scm.scm_unittest:
  Traceback (most recent call last):
  Traceback (most recent call last):
    File "/Volumes/gsnedders/projects/Safari/OpenSource/Tools/Scripts/webkitpy/test/main.py", line 290, in _check_imports
    File "/Volumes/gsnedders/projects/Safari/OpenSource/Tools/Scripts/webkitpy/test/main.py", line 290, in _check_imports
      __import__(name)
      __import__(name)
    File "/Volumes/gsnedders/projects/Safari/OpenSource/Tools/Scripts/webkitpy/common/checkout/scm/scm_unittest.py", line 38, in <module>
    File "/Volumes/gsnedders/projects/Safari/OpenSource/Tools/Scripts/webkitpy/common/checkout/scm/scm_unittest.py", line 38, in <module>
      import pathlib
      import pathlib
  ImportError: No module named pathlib
  ImportError: No module named pathlib

As part of my medium-term goal of migrating us to using pytest where we're likely to skip specific slow tests rather than merely doing this at a module level, we should make sure this is importable.

[Sam Sneddon [:gsnedders]]

Created attachment 426142 [details]
Patch

[EWS]

Committed r276083 (236595@main): <https://commits.webkit.org/236595@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 426142 [details].

[Ryan Haddad]

rdar://76735334