Fix breaking change with dropped support for userids with colons (#3572)

* Fix breaking change with dropped support for userids with colons

* Add tests for users with colons

Author: sambhav

kinto/core/initialization.py

@@ -475,8 +475,9 @@ def on_new_response(event):
         # Count unique users.
         user_id = request.prefixed_userid
         if user_id:
-            # Get rid of colons in metric packet (see #1282).
-            auth, user_id = user_id.split(":")
+            auth, user_id = user_id.split(":", 1)
+            # Get rid of colons in metric packet (see #1282 and  #3571).
+            user_id = user_id.replace(":", ".")
             metrics_service.count("users", unique=[("auth", auth), ("userid", user_id)])
 
         status = event.response.status_code

tests/core/test_initialization.py

@@ -382,6 +382,16 @@ def test_statsd_counts_unique_users(self, digest_mocked):
             "users", unique=[("auth", "basicauth"), ("userid", "mat")]
         )
 
+    @mock.patch("kinto.core.utils.hmac_digest")
+    def test_statsd_counts_unique_users_with_colons(self, digest_mocked):
+        digest_mocked.return_value = "user:with:colons"
+        kinto.core.initialize(self.config, "0.0.1", "settings_prefix")
+        app = webtest.TestApp(self.config.make_wsgi_app())
+        app.get("/v0/", headers=get_user_headers("user:with:colons"))
+        self.mocked().count.assert_any_call(
+            "users", unique=[("auth", "basicauth"), ("userid", "user.with.colons")]
+        )
+
     def test_statsd_counts_authentication_types(self):
         kinto.core.initialize(self.config, "0.0.1", "settings_prefix")
         app = webtest.TestApp(self.config.make_wsgi_app())