Code review comment for lp:~jtv/launchpad/bug-526462

Thanks! I did start out thinking that one check should be enough. I ended up with one that might produce false positives, plus one that might produce false negatives. For that situation, a --force against false positives plus a final just-in-case safeguard seemed the right approach. In any case the check is easy; maybe someday we'll build reusable helpers for this.