Fix dependency issues

We haven't bumped the test version for a while.
Also bumped the version of Flask and itsdangerous.
In order to fix flask warnings I needed to changed how the blueprints were registerd.

tests/app/v2/test_errors.py

@@ -128,7 +128,5 @@ def test_bad_method(app_for_test):
 
             assert response.status_code == 405
 
-            assert response.json == {
-                "result": "error",
-                "message": "The method is not allowed for the requested URL."
-            }
+            assert response.get_data(as_text=True) == \
+                   '{"message":"The method is not allowed for the requested URL.","result":"error"}\n'