Raise an error if module import fails.

Previously a missing module would cause the config file generator
to pass (mostly) silently with only a small message going to
stdout. If we can't import a module that seems like it is a bad
thing so lets just bail.

Change-Id: I391220e1344ba1785bf04654c7c5f52e2e8e82fc
Merge "Raise an error if module import fails."