Added a failing test when using pickle with signal hooks

tests/fixtures.py

@@ -1,6 +1,8 @@
+import pickle
 from datetime import datetime
 
 from mongoengine import *
+from mongoengine import signals
 
 
 class PickleEmbedded(EmbeddedDocument):
@@ -15,6 +17,24 @@ class PickleTest(Document):
     photo = FileField()
 
 
+class PickleSignalsTest(Document):
+    number = IntField()
+    string = StringField(choices=(('One', '1'), ('Two', '2')))
+    embedded = EmbeddedDocumentField(PickleEmbedded)
+    lists = ListField(StringField())
+
+    @classmethod
+    def post_save(self, sender, document, created, **kwargs):
+    	pickled = pickle.dumps(document)
+
+    @classmethod
+    def post_delete(self, sender, document, **kwargs):
+    	pickled = pickle.dumps(document)
+
+signals.post_save.connect(PickleSignalsTest.post_save, sender=PickleSignalsTest)
+signals.post_delete.connect(PickleSignalsTest.post_delete, sender=PickleSignalsTest)
+
+
 class Mixin(object):
     name = StringField()