Resolve "Provide base templates for e-mails generated by apps"

Closes #439 (closed)

aleksis/core/celery.py

 import os
+from traceback import format_exception
 
 from django.conf import settings
 
@@ -17,7 +18,7 @@ app.autodiscover_tasks()
 
 @task_failure.connect
 def task_failure_notifier(
-    sender=None, task_id=None, exception=None, args=None, traceback=None, **kwargs
+    sender=None, task_id=None, exception=None, args=None, kwargs=None, traceback=None, **__
 ):
     recipient_list = [e[1] for e in settings.ADMINS]
     send_email(
@@ -29,8 +30,8 @@ def task_failure_notifier(
             "task": str(sender),
             "task_id": str(task_id),
             "exception": str(exception),
-            "args": str(args),
-            "kwargs": str(kwargs),
-            "traceback": str(traceback),
+            "args": args,
+            "kwargs": kwargs,
+            "traceback": "".join(format_exception(type(exception), exception, traceback)),
         },
     )