prevent database flush from deleting collections

TransactionTestCase does a flush between tests leading to all tests except
the first one not to have all the collections present.

Author: timgraham

django_mongodb/operations.py

@@ -175,7 +175,7 @@ def execute_sql_flush(self, tables):
             collection = self.connection.database[table]
             options = collection.options()
             if not options.get("capped", False):
-                collection.drop()
+                collection.delete_many({})
 
     def prep_lookup_value(self, value, field, lookup):
         """