bump dependency versions, fix tests and deprecation warnings

gnuviechadmin/managemails/admin.py

@@ -1,7 +1,7 @@
 from django.utils.html import format_html
 from django.contrib import admin
 from django import forms
-from django.forms.util import flatatt
+from django.forms.utils import flatatt
 from django.utils.translation import ugettext as _
 
 from .models import (