fix extend

Author: antgonza

qtp_job_output_folder/tests/test_summary.py

@@ -61,9 +61,8 @@ def test_summary(self):
         # asserting content of html
         res = self.qclient.get("/qiita_db/artifacts/%s/" % aid)
         # cleaning artifact files, to avoid errors
-        [self._clean_up_files.extend(ff['filepath'])
+        [self._clean_up_files.extend([ff['filepath']])
          for f in res['files'].values() for ff in f]
-        print(self._clean_up_files)
         html_fp = res['files']['html_summary'][0]['filepath']
         with open(html_fp) as html_f:
             html = html_f.read()