Better error checking when calling filename_matcher

Right now it looks like any exception causes a hang.

Hey @thatch! Can you share more information on the error? I am a first time contributor. And I would love to give it a try.

Sure! Using a bowler script something like sample.py

from bowler import Query

def filename_matcher(*args):
  raise Exception()

Query(["."], filename_matcher=filename_matcher).diff()

and run with

bowler run sample.py

It should print the exception once per file, and exit. Right now it causes a hang. @jreese any further advice?

Is this issue still open? If its open I would like to contribute