convert: raise Abort instead of NoRepo when CVS pserver auth fails.
At this point we know the source is CVS, so we should not go through
the rest of the converters.
Is there an error message when trying to diff non-existing files?
found: No such file or directory
not: No such file or directory
Is there an error message when trying to add non-existing files?
found: No such file or directory
not: No such file or directory