Fix typo in extract_verses_by_meter.py

scripts/extract_verses_by_meters.py

@@ -29,7 +29,7 @@ def main(hypotactic_dir, top_out_dir, meters=['hexameter']):
                         json.dump(verses_for_meter, f)
         except Exception:
             print('ERROR at document {}'.format(document.title),
-                  file=sys.stdderr)
+                  file=sys.stderr)
             traceback.print_exc()