Revert Context iter changes in 87dc1a44b2 and fix a f-string

Closes #185

mautrix_telegram/context.py

@@ -38,7 +38,10 @@ class Context:
         self.session_container = session_container  # type: AlchemySessionContainer
         self.public_website = public_website  # type: PublicBridgeWebsite
         self.provisioning_api = provisioning_api  # type: ProvisioningAPI
-        self.t = (self.az, self.db, self.config, self.loop, self.bot)
 
     def __iter__(self):
-        return iter(self.t)
+        yield self.az
+        yield self.db
+        yield self.config
+        yield self.loop
+        yield self.bot

mautrix_telegram/matrix.py

@@ -208,7 +208,7 @@ class MatrixHandler:
             self.log.debug(f"Ignoring message \"{message}\" from {sender} to {room}:"
                            " User is not whitelisted.")
             return
-        self.log.debug("Received Matrix event \"{message}\" from {sender} in {room}")
+        self.log.debug(f"Received Matrix event \"{message}\" from {sender} in {room}")
 
         portal = Portal.get_by_mxid(room)
         if not is_command and portal and (await sender.is_logged_in() or portal.has_bot):