1) Log into Treeherder as someone with is_staff set 2) Visit https://treeherder.mozilla.org/admin/auth/user/ 3) Select a user and try to modify them (eg change their is_staff bit, or mark the user as disabled) Expected: Works Actual: Form submission fails with error: "Enter a valid username. This value may contain only English letters, numbers, and @/./+/-/_ characters." This is due to the forward slash in the username from the `mozilla-ldap/` or `email/` prefixes. I'm guessing that to fix this we'd need to subclass the Django user model and adjust the form validation on that field. In the meantime the workaround is to edit the auth_user table manually on the DB.

Wontfix since we're removing Django admin in bug 1065784.