Just fatal for any setting of open_basedir

Summary:
Fixes T11627.

Beyond being complex, I have no real reason to believe these checks even work (and they don't test repositories, file storage, logfiles, etc).

Test Plan:
Faked the error:

{F1813433}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11627

Differential Revision: https://secure.phabricator.com/D16544