If one adds a user with nimbus-new-user, then removes that user with nimbus-remove-user, then attempts to re-add the user yet again, a failure occurs. It seems that repeated additions and removals of a user with a particular email address fails because there is a trace of the user left behind in the nimbus.sqlite database (in the auth_user table). This entry might be made when the --web option is used with nimbus-new-user utility.
Add an option to remove the webapp user
nimbus-remove-user did not allow to remove a user from the webapp.
Since the user was still in the webapp DB, it could not be added again.
nimbus-remove-user now has -W and -w options to remove entries from the