Originally brought up on the list, but making an Issue so we don't forget.
When IPython is re-routed behind a prefix (e.g. /ipython/), the login url is hardcoded, and will always fail, so if you are using a prefix, you cannot also use a password.
allows password and prefix for notebook
allows both password and prefix for notebook
backported to 0.13.1 from PR #2073
Backport PR #2073: allows password and prefix for notebook