UPD: improved workflow code.

dav_events/apps.py

@@ -1,7 +1,6 @@
 from django.core.exceptions import ImproperlyConfigured
 
 from . import signals
-from . import workflow
 from .config import AppConfig as _AppConfig, DefaultSetting
 
 DEFAULT_SETTINGS = (
@@ -32,5 +31,6 @@ class AppConfig(_AppConfig):
     default_settings = DEFAULT_SETTINGS
 
     def ready(self):
+        from .workflow import workflow
         signals.event_updated.connect(workflow.send_emails_on_event_update)
         signals.event_status_updated.connect(workflow.send_emails_on_event_status_update)