Plugin hangs when scp credentials are incorrect

I was trying to follow the New Release Process (which requires staging to an alternate repository). On account of this, I accidentally used an scp url with incorrect credentials; the forked Maven process hung waiting for me to enter credentials on the command line. Unfortunately, there's no visible sign of this on the console of the forking process, and no way to type the answer to any questions; all you can do at that point is Ctrl-C.

The forked Maven should automatically halt if it doesn't have credentials it needs. (For example, are we correctly passing in -B to prevent keyboard authorization?)