Implement MIT signups.

Here we introduce a new manage.py command, activate_mit, which takes a
number of usernames and sends out emails to the users with instructions on
how to activate their accounts.

(imported from commit f14401b55f915698e83ff27b86434f53e64685f3)

zephyr/forms.py

@@ -10,6 +10,13 @@ def is_unique(value):
     except User.DoesNotExist:
         pass
 
+def is_active(value):
+    try:
+        if User.objects.get(email=value).is_active:
+            raise ValidationError(u'%s is already active' % value)
+    except User.DoesNotExist:
+        pass
+
 class UniqueEmailField(forms.EmailField):
     default_validators = [validators.validate_email, is_unique]