Hi all - I'm trying to use external user authentication with Galaxy.  The external authentication passes to Galaxy the username with the mail domain at HTTP_USER. 

In galaxy.ini, I enable:
use_remote_user = True

When I try to access Galaxy, I get the message:
Galaxy is configured to authenticate users via an external method (such as HTTP authentication in Apache), but a username was not provided by the upstream (proxy) server. This is generally due to a misconfiguration in the upstream server.

But nothing in paster.log indicating what the error is. 

How do I track this down?