Prevent hacking.py from crashing on unexpected import exception

If a module isn't importable due to an unexpected error during
__import__.  Ignore it, hacking.py is only a style checker.

Fix bug 1134622

Change-Id: I704b7cc9a7bd415018ae7634767b7bd9c3b7d9b2
Merge "Prevent hacking.py from crashing on unexpected import exception"