exclude some fields from conversion

backend.py

@@ -36,6 +36,11 @@ class EventManDB(object):
             'increment': '$inc'
     }
 
+    _force_conversion = {
+            'seq_hex': str,
+            'persons.seq_hex': str
+    }
+
     def __init__(self, url=None, dbName='eventman'):
         """Initialize the instance, connecting to the database.
 
@@ -100,7 +105,10 @@ class EventManDB(object):
         if isinstance(seq, dict):
             d = {}
             for key, item in seq.iteritems():
-                d[key] = self.convert(item)
+                if key in self._force_conversion:
+                    d[key] = self._force_conversion[key](item)
+                else:
+                    d[key] = self.convert(item)
             return d
         if isinstance(seq, (list, tuple)):
             return [self.convert(x) for x in seq]

eventman_server.py

@@ -383,7 +383,7 @@ class EventsHandler(CollectionHandler):
                 doc.get('persons') or [])
         env = self._dict2env(new_person_data)
         if person_id is None:
-            person_id = new_person_data.get('person_id')
+            person_id = str(new_person_data.get('person_id'))
         env.update({'PERSON_ID': person_id, 'EVENT_ID': id_, 'EVENT_TITLE': doc.get('title', '')})
         stdin_data = {'old': old_person_data,
             'new': new_person_data,