Cannot upgrade room with malformed PL event

[richvdh]

Some rooms have malformed power-levels events. Upgrading such a room can result in errors such as:

2022-04-24 07:26:33,207 - synapse.http.server - 104 - ERROR - POST-17431419 - Failed handle request via 'RoomUpgradeRestServlet': <XForwardedForRequest at 0x7f2066147418 method='POST' uri='/_matrix/client/r0/rooms/!room%3Amatrix.org/upgrade' clientproto='HTTP/1.1' site='8080'>
Capture point (most recent call last):
  File "/usr/local/lib/python3.7/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/local/lib/python3.7/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/synapse/src/synapse/app/homeserver.py", line 460, in <module>
    main()
  File "/home/synapse/src/synapse/app/homeserver.py", line 456, in main
    run(hs)
  File "/home/synapse/src/synapse/app/homeserver.py", line 442, in run
    logger=logger,
  File "/home/synapse/src/synapse/app/_base.py", line 180, in start_reactor
    run()
  File "/home/synapse/src/synapse/app/_base.py", line 162, in run
    run_command()
  File "/home/synapse/env-py37/lib/python3.7/site-packages/twisted/internet/base.py", line 1315, in run
    self.mainLoop()
  File "/home/synapse/env-py37/lib/python3.7/site-packages/twisted/internet/base.py", line 1325, in mainLoop
    reactorBaseSelf.runUntilCurrent()
  File "/home/synapse/env-py37/lib/python3.7/site-packages/twisted/internet/base.py", line 964, in runUntilCurrent
    f(*a, **kw)
  File "/home/synapse/src/synapse/storage/databases/main/events_worker.py", line 914, in fire
    d.callback(row_dict)
  File "/home/synapse/env-py37/lib/python3.7/site-packages/twisted/internet/defer.py", line 661, in callback
    self._startRunCallbacks(result)
  File "/home/synapse/env-py37/lib/python3.7/site-packages/twisted/internet/defer.py", line 763, in _startRunCallbacks
    self._runCallbacks()
  File "/home/synapse/env-py37/lib/python3.7/site-packages/twisted/internet/defer.py", line 858, in _runCallbacks
    current.result, *args, **kwargs
  File "/home/synapse/env-py37/lib/python3.7/site-packages/twisted/internet/defer.py", line 1750, in gotResult
    current_context.run(_inlineCallbacks, r, gen, status)
Traceback (most recent call last):
  File "/home/synapse/env-py37/lib/python3.7/site-packages/twisted/internet/defer.py", line 1660, in _inlineCallbacks
    result = current_context.run(gen.send, result)
  File "/home/synapse/src/synapse/util/caches/response_cache.py", line 246, in cb
    return await callback(*args, **kwargs)
  File "/home/synapse/src/synapse/handlers/room.py", line 270, in _upgrade_room
    tombstone_event_id=tombstone_event.event_id,
  File "/home/synapse/src/synapse/handlers/room.py", line 475, in clone_existing_room
    initial_state[(EventTypes.PowerLevels, "")]
  File "/home/synapse/src/synapse/events/utils.py", line 597, in copy_power_levels_contents
    "Invalid power_levels value for %s.%s: %r" % (k, k1, v1)
TypeError: Invalid power_levels value for users.@example:matrix.org: '0'

[richvdh]

I'm not sure if the correct behaviour here is to ignore such malformed entries, or to pass them through int().

Related: #1237, matrix-org/matrix-spec#853

[richvdh]

The work to be done here is to update copy_power_levels_contents to tolerate stringy PL event values (and convert them to ints).