Fix FileNotFoundError invocation in Git SCMTool

Review Request #9901 — Created May 2, 2018 and submitted — Latest diff uploaded

Information

Review Board
release-2.5.x
ffff95e...

Reviewers

The Git SCMTool was providing the commit SHA to the FileNotFoundError,
leading to misleading error messages. This has been fixed.

Triggered a FileNotFoundError in a Git repository and saw the correct
error message.