BridgeDB should be able to arbitrarily blacklist bad bridges
I believe that the bad-exit file for relays is in the format:
FINGERPRINT [SP REASON]
where REASON may contain more whitespace. Whatever that format is, BridgeDB should probably just copy that to avoid needing extra parsers in other pieces of infrastructure in the future.
I'm going to implement this to blacklist bridges like the "ki" sybils.