username collision when upgrading

Created by: repsejnworb

The "work out a username based on the email"-feature doesn't work very well if there are several users with the same initializing name in their email:

leeroy.jenkins@example.com leeroy.jenkins@fish.net

This would cause: Usernames for users:rake aborted! Validation failed: Username has already been taken

After this error you will have to set the username of any user where it was already set to NULL and you also have to remove and namespace that was created for any user, else you run into: Usernames for users:rake aborted! Validation failed: Path has already been taken