Description: revert a change that requires Python 3.6 (https://docs.python.org/3/whatsnew/3.6.html#whatsnew36-pep487)
Author: Olivier Tilloy <olivier.tilloy@canonical.com>

--- a/third_party/python/glean_parser/glean_parser/metrics.py
+++ b/third_party/python/glean_parser/glean_parser/metrics.py
@@ -15,6 +15,8 @@ from typing import Any, Dict, List, Opti
 from . import pings
 from . import util
 
+import pep487
+
 
 # Important: if the values are ever changing here, make sure
 # to also fix mozilla/glean. Otherwise language bindings may
@@ -32,7 +34,7 @@ class DataSensitivity(enum.Enum):
     highly_sensitive = 4
 
 
-class Metric:
+class Metric(pep487.PEP487Object):
     typename = "ERROR"
     glean_internal_metric_cat = "glean.internal.metrics"
     metric_types = {}