If no tags are given, we maintain them

apps/rp/tests/test_article.py

@@ -256,8 +256,8 @@ class TestArticleApi(TestCase):
         # Need to test if we keep the tags
         r = self.client.post('/api/articles/',
                              {'url': a.url, 'title': a.title,
-                              'tags': ''
-                              })
+                              },
+                             format='json')
         assert list(a.tags.all().values('name')) == [json.loads(t) for t in r.data['tags']]
 
     def test_api_recover(self):