Fixed #3435 -- Fixed serializing to a file stream. Patch from SmileyChris.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@5075 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/serializers/base.py

@@ -105,8 +105,10 @@ class Serializer(object):
 
     def getvalue(self):
         """
-        Return the fully serialized queryset.
+        Return the fully serialized queryset (or None if the output stream is
+        not seekable).
         """
+        if callable(getattr(self.stream, 'getvalue', None)):
             return self.stream.getvalue()
 
 class Deserializer(object):

django/core/serializers/json.py

@@ -19,6 +19,7 @@ class Serializer(PythonSerializer):
         simplejson.dump(self.objects, self.stream, cls=DateTimeAwareJSONEncoder, **self.options)
 
     def getvalue(self):
+        if callable(getattr(self.stream, 'getvalue', None)):
             return self.stream.getvalue()
 
 def Deserializer(stream_or_string, **options):