Fix STDERR from appearing with test_content, remove Asyncnbviewertestcase because it's never used

Author: krinsman

nbviewer/providers/url/tests/test_content.py

@@ -1,14 +1,14 @@
 # -*- coding: utf-8 -*-
 
-from ....tests.async_base import AsyncNbviewerTestCase
+import requests
+from ....tests.base import NBViewerTestCase
 
-
-class ForceUTF8TestCase(AsyncNbviewerTestCase):
+class ForceUTF8TestCase(NBViewerTestCase):
     def test_utf8(self):
         """ #507, bitbucket returns no content headers, but _is_ serving utf-8
         """
-        response = self.fetch(
-            '/urls/bitbucket.org/sandiego206/asdasd/raw/master/Untitled.ipynb'
+        response = requests.get(
+            self.url('/urls/bitbucket.org/sandiego206/asdasd/raw/master/Untitled.ipynb')
         )
-        self.assertEqual(response.code, 200)
-        self.assertIn("ñ", response.body)
+        self.assertEqual(response.status_code, 200)
+        self.assertIn("ñ", response.content)