Factor out checks over whether a file can be processed.
Factor out checks over whether a file can be processed.

Issue #86

HackBrexit/MinistersUnderTheInfluence,HackBrexit/MinistersUnderTheInfluence,HackBrexit/MinistersUnderTheInfluence,HackBrexit/MinistersUnderTheInfluence,HackBrexit/MinistersUnderTheInfluence,HackBrexit/MinistersUnderTheInfluence