http://www.djangosnippets.org/snippets/1822/

login_as_anybody_in_django.py

def login_using_email(request, email):
    '''DONT EVER USE this method for normal purposes. This is only there, for debugging specific problems related to users'''
    from django.contrib.auth import get_backends
    backend = get_backends()[0]
    from django.contrib.auth.models import User
    user = User.objects.get(email=email)
    user.backend = "%s.%s" % (backend.__module__, backend.__class__.__name__)
    from django.contrib.auth import login as django_login
    django_login(request, user)
    #set_any_extra_session_variables(request)