show a nice success message after editing theme

apps/devhub/views.py

@@ -323,6 +323,7 @@ def edit_theme(request, addon_id, addon, theme=False):
                                      request=request, instance=addon)
     if request.method == 'POST' and form.is_valid():
         form.save()
+        messages.success(request, _('Changes successfully saved.'))
         return redirect('devhub.themes.edit', addon.reload().slug)
     return jingo.render(request, 'devhub/personas/edit.html', {
         'addon': addon,

mkt/submit/urls.py

@@ -3,10 +3,8 @@ from django.shortcuts import redirect
 
 from lib.misc.urlconf_decorator import decorate
 
-from addons.urls import ADDON_ID
 import amo
 from amo.decorators import write
-from devhub import views as devhub_views
 from . import views
 
 

mkt/submit/views.py

@@ -5,7 +5,6 @@ from django.utils.translation.trans_real import to_language
 
 import commonware.log
 import jingo
-from waffle.decorators import waffle_switch
 
 import amo
 from amo.decorators import login_required