Fix raven integration

src/pretix/sentry.py

@@ -0,0 +1,41 @@
+from threading import Lock
+
+from raven.contrib.celery import SentryCeleryHandler
+from raven.contrib.django.apps import RavenConfig
+from raven.contrib.django.models import (
+    SentryDjangoHandler, client, get_client, install_middleware,
+    register_serializers,
+)
+
+_setup_lock = Lock()
+
+_initialized = False
+
+
+class CustomSentryDjangoHandler(SentryDjangoHandler):
+    def install_celery(self):
+        self.celery_handler = SentryCeleryHandler(client, ignore_expected=True).install()
+
+
+def initialize():
+    global _initialized
+
+    with _setup_lock:
+        if _initialized:
+            return
+
+        register_serializers()
+        install_middleware()
+
+        handler = CustomSentryDjangoHandler()
+        handler.install()
+
+        # instantiate client so hooks get registered
+        get_client()  # NOQA
+
+        _initialized = True
+
+
+class App(RavenConfig):
+    def ready(self):
+        initialize()