fix issue where churn output isn't captured on error which leads to metr...

...ic fu crashing opposed to just empty churn reports. Churn requires one of 4 source control systems to exists but it can be safely left out of the report on that error. It will print error to concole when running to alert users to the issue...


This deals with the case where no source control system is found for churn. It requires any of a few different source control systems to be available to check on the churn. This change makes it output the error to the console when metric fu is run, but it doesn't crash metric fu. It will detect that it didn't collect the churn output and just have a empty churn report for the project.

resolves: metricfu#65