Unit test enabled for list_runs (#817)

* unit test enabled for list runs

for issue openml/OpenML#948

* change previous commit with pep8 changes

Author: prabhant

tests/test_runs/test_run_functions.py

@@ -1243,9 +1243,9 @@ def test_get_runs_list_by_filters(self):
 
         runs = openml.runs.list_runs(id=ids, task=tasks, uploader=uploaders_1)
 
-    @unittest.skip("API currently broken: https://github.com/openml/OpenML/issues/948")
     def test_get_runs_list_by_tag(self):
         # TODO: comes from live, no such lists on test
+        # Unit test works on production server only
         openml.config.server = self.production_server
         runs = openml.runs.list_runs(tag='curves')
         self.assertGreaterEqual(len(runs), 1)