Invalidate user sessions after password update

Fixes #984

Author: berkerpeksag

pydotorg/settings/base.py

@@ -103,6 +103,7 @@
     'django.contrib.sessions.middleware.SessionMiddleware',
     'django.middleware.csrf.CsrfViewMiddleware',
     'django.contrib.auth.middleware.AuthenticationMiddleware',
+    'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
     'django.contrib.messages.middleware.MessageMiddleware',
     'waffle.middleware.WaffleMiddleware',
     'django.middleware.clickjacking.XFrameOptionsMiddleware',