Fill in get_metrics_manager() on port db MockHomeserver

synapse/_scripts/synapse_port_db.py

@@ -58,6 +58,7 @@ from synapse.logging.context import (
     make_deferred_yieldable,
     run_in_background,
 )
+from synapse.metrics.homeserver_metrics_manager import HomeserverMetricsManager
 from synapse.notifier import ReplicationNotifier
 from synapse.storage.database import DatabasePool, LoggingTransaction, make_conn
 from synapse.storage.databases.main import FilteringWorkerStore
@@ -308,6 +309,7 @@ class Store(
 class MockHomeserver:
     def __init__(self, config: HomeServerConfig):
         self.clock = Clock(reactor)
+        self.metrics_manager = HomeserverMetricsManager()
         self.config = config
         self.hostname = config.server.server_name
         self.version_string = SYNAPSE_VERSION
@@ -315,6 +317,9 @@ class MockHomeserver:
     def get_clock(self) -> Clock:
         return self.clock
 
+    def get_metrics_manager(self) -> HomeserverMetricsManager:
+        return self.metrics_manager
+
     def get_reactor(self) -> ISynapseReactor:
         return reactor