Don't require explicit backend import (Closes: #41)

Signed-off-by: Chris Lamb <chris@chris-lamb.co.uk>

django_slack/backends.py

@@ -40,22 +40,17 @@ class DisabledBackend(Backend):
     def send(self, url, data):
         pass
 
-try:
-    from celery import shared_task
-except ImportError:
-    pass
-else:
-    @shared_task
-    def celery_send(*args, **kwargs):
-        import_string(app_settings.BACKEND_FOR_QUEUE)().send(*args, **kwargs)
-
-    class CeleryBackend(Backend):
-        def __init__(self):
-            # Check we can import our specified backend up-front
-            import_string(app_settings.BACKEND_FOR_QUEUE)()
-
-        def send(self, *args, **kwargs):
-            # Send asynchronously via Celery
-            celery_send.delay(*args, **kwargs)
+class CeleryBackend(Backend):
+    def __init__(self):
+        # Lazily import to avoid dependency
+        from .tasks import send
+        self.send = send
+
+        # Check we can import our specified backend up-front
+        import_string(app_settings.BACKEND_FOR_QUEUE)()
+
+    def send(self, *args, **kwargs):
+        # Send asynchronously via Celery
+        self.send.delay(*args, **kwargs)
 
 Urllib2Backend = UrllibBackend # For backwards-compatibility

django_slack/tasks.py

@@ -0,0 +1,9 @@
+from celery import task
+
+from django.utils.module_loading import import_string
+
+from .app_settings import app_settings
+
+@task
+def send(*args, **kwargs):
+    import_string(app_settings.BACKEND_FOR_QUEUE)().send(*args, **kwargs)