extensions: avoid a crash when the version isn't properly byteified on py3 We already force bytestr on the `testedwith` and `buglink` attributes in dispatch.py when generating a bug report with a similar comment about not every extension being ported to py3. We should do the same here, so the function can be properly typed. Differential Revision: https://phab.mercurial-scm.org/D9433