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.
% basic
% unknown
*** [alias] unknown: command bargle is unknown
% ambiguous
*** [alias] ambiguous: command s is ambiguous
% recursive
*** [alias] recursive: circular dependency on recursive
adding foo
% with opts
C foo