Names show up multiple times in assignment pulldown
1. Go to an event.
2. Try to assign to assign to someone other than yourself.
3. Selection dialog with pulldown appears so that you can choose person.
4. Some names (currently Greg Wilson and Tracy Teal, possibly others) show up multiple times in that list.

diff --git a/workshops/lookups.py b/workshops/lookups.py
index 2fef53b0..8f1108d3 100644
--- a/workshops/lookups.py
+++ b/workshops/lookups.py
@@ -83,7 +83,7 @@ class AdminLookup(ModelLookup):
         admin_group = Group.objects.get(name='administrators')
         results = results.filter(
             Q(is_superuser=True) | Q(groups__in=[admin_group])
-        )
+        ).distinct()
         return results
 
 
['workshops/lookups.py']