Django authentication fails with DatabaseError

Question

My Django app is deployed on Heroku and I'm using Postgres there and MySQL for development. I can't get the user to login (manually) and I get this error:

DatabaseError at /login/
current transaction is aborted, commands ignored until end of transaction block

After examining the code, it turned out that the problem happens in the django.contrib.auth.authenticate

Here is my view's code:

if request.method == 'POST':
        username = request.POST.get('username')
        print username
        password = 'none'

        try:
            user = User.objects.create_user(username, 'none', password)
            user.save()
            print user
            fb_user_id = request.POST.get('fb_user_id')
            print fb_user_id
            full_name = request.POST.get('full_name')
            print full_name
            hostname = request.get_host()
            invite_link = hostname + '/referal/'+str(short_url.encode_url(int(fb_user_id)))
            print invite_link
            # Create a UserProfile object that references user.
            profile = UserProfile(
                user = user,
                fb_user_id = fb_user_id,
                username = username,
                full_name = full_name,
                invite_link = invite_link
                )
            profile.save()
            print profile

            settings = Setting(user=profile)
            settings.save()
            print settings
            print "success"

            return HttpResponse('success')
        except:
            print "error"

        # Authenticate the user
        user = authenticate(username=username,password='none')
        print user
        if user is not None:
            print "user is not None: ", user
            if user.is_active:
                print "loggin user in "
                login(request, user)
                return HttpResponseRedirect('/')
        else:
            print user,
            print "user is none"


    else:
        return HttpResponse('not a post ')
    return HttpResponse('fail')

When i try to login with registered users, the last thing i see in the log is "error" which is printed in the except block. In development environment, everything works as expected ! Did anybody run into this problem before?

EDIT Actually the authentication through the admin panel works just fine, and the registration of users works perfectly too.