Comment 4 for bug 93609

The recent lp:/// work does make this better, but it doesn't fix it. Specifically, there's no reference to a place to get help, and "bzr: ERROR: Invalid url supplied to transport:" doesn't _really_ add any value to the message that the user sees.

I think the correct fix is to define a special exception class for BadLaunchpadURL.

Note that the flaw in the 'cannot push to new branch' message will be corrected by making it possible to push to new branches.

Re-assigning to Bazaar, since that's where the code change needs to happen.