UWSGI adding double slash to admin login form in Django
After a long time I've figured out what the problem is! I had followed some directions on how to set up uwsgi with nginx that said to include a line saying uwsgi_param SCRIPT_NAME /;.  The purpose of SCRIPT_NAME is to provide the base path for the UWSGI application, so in this case it serves to double the slashes. I found the same problem occurring in pyramid. I suspect this will occur with any UWSGI application.
Running Django behind UWSGI, I have set up an instance of Mezzanine that is almost working perfectly.  The only problem is the admin login page does not work properly.  If you just try to log in normally than the browser is redirected to http://admin/.  The html form action attribute is set to //admin/ instead of /admin/ so the browser sees "admin" as being a domain name instead of a root directory of the current domain.
I've tried wading through the Django and Mezzanine package codes, but I can't see anything in there that should be causing an extraneous slash.  I found one web page saying that changing settings.FORCE_SCRIPT_NAME to "/" could cause this, but I am not overriding the default value of None so this shouldn't be the cause.
In urls.py I have the following (which I think is the default):

urlpatterns = patterns("",

    # Change the admin prefix here to use an alternate URL for the
    # admin interface, which would be marginally more secure.
    ("^admin/", include(admin.site.urls)),

  ....