Add missing import

Author: mhagander

postgresqleu/confreg/mail.py

@@ -4,6 +4,7 @@
 from django.http import Http404, HttpResponse, HttpResponseRedirect
 from django.contrib import messages
 from django.utils import timezone
+from django.forms.utils import ErrorDict
 
 
 from postgresqleu.util.db import exec_to_dict, exec_to_scalar, exec_no_result