Ensure query_dict is a dict after the contents have been modified.

_fix_query_dict modifies its argument in place. Ensure that the
argument passed in has a local name and will be passed into the
subsequent filter_by call.

mediagoblin/db/sql/base.py

@@ -51,12 +51,18 @@ class GMGTableBase(object):
     query = Session.query_property()
 
     @classmethod
-    def find(cls, query_dict={}):
+    def find(cls, query_dict=None):
+        if query_dict is None:
+            query_dict = {}
+
         _fix_query_dict(query_dict)
         return cls.query.filter_by(**query_dict)
 
     @classmethod
-    def find_one(cls, query_dict={}):
+    def find_one(cls, query_dict=None):
+        if query_dict is None:
+            query_dict = {}
+
         _fix_query_dict(query_dict)
         return cls.query.filter_by(**query_dict).first()