show exceptions in plain text, not HTML

lib/middleware/exceptions.py

@@ -0,0 +1,8 @@
+import traceback
+from django.http import HttpResponse
+
+class ExceptionMiddleware(object):
+
+    def process_exception(self, request, exception):
+        return HttpResponse(traceback.format_exc(exception), content_type="text/plain", status=500)
+