Assert that Serializer was initialized with data=something in is_valid() #2228
Description
>>> serializer = SnippetSerializer(snippet)
>>> serializer.is_valid()
False
>>> serializer.errors
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "/Users/loic/Dev/django-rest-framework/rest_framework/serializers.py", line 429, in errors
return ReturnDict(ret, serializer=self)
File "/Users/loic/Dev/django-rest-framework/rest_framework/utils/serializer_helpers.py", line 13, in __init__
super(ReturnDict, self).__init__(*args, **kwargs)
File "/usr/local/Cellar/python/2.7.8_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/collections.py", line 52, in __init__
self.__update(*args, **kwds)
File "/Users/loic/Dev/rest_tutorial/./.venv/bin/../lib/python2.7/_abcoll.py", line 566, in update
for key, value in other:
ValueError: too many values to unpack