You can partially register an already existing username

1. Go to http://hackage.haskell.org/users/register-request
2. For login username, choose an already existing username
3. You get a registration email sent to you regardless.

It seem that hackage doesn't currently check to see if the user is already registered before sending the email - as a result, registration emails are sent unconditionally. Upon clicking said email, and entering a password, you are greeted with something like "looks like somebody already registered this username".

Instead, the behavior should be that if a login username already exists, you're told that it does upon attempt at registration, not upon email validation.

I'm willing to take a shot at a PR, once confirmed.