Code review comment for ~chad.smith/cloud-init:tools/migrate-script

I re-ran, and the error message isn't clear about which remote (github or launchpad) has the existing branches.

So we should prefix each error with the host.

Also, it appears to be changing into a new branch under the covers, the migrate-lp-to-github; so we should emit that we're creating a local branch and the name when we do it, and pushing to github, etc.

And I think we should emit the git commands used to reset things:

git push <remote> --delete migrate-lp-to-github

or have the script do this for users.