+smut to answer if this is WAI.

Not working as intended, but I also haven't changed anything I don't think. The bots are getting 500s downloading the bot code:
[I2018-05-22T15:56:15.920724-07:00 6661 0 main.go:153] Downloading: /b/s/swarming_bot.zip.
[E2018-05-22T15:56:16.130533-07:00 6661 0 main.go:352] unexpected HTTP status: 500 Internal Server Error

From the server:
[Errno 2] No such file or directory: '/base/data/home/apps/s~chromium-swarm-dev/3561-435d49c-tainted-smut.409815868790738271/swarming_bot/client/named_cache.py' (/base/alloc/tmpfs/dynamic_runtimes/python27/277b61042b697c7a_unzipped/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py:1552)
Traceback (most recent call last):
  File "third_party/webapp2-2.5.2/webapp2.py", line 1535, in __call__
    rv = self.handle_exception(request, response, e)
  File "third_party/webapp2-2.5.2/webapp2.py", line 1529, in __call__
    rv = self.router.dispatch(request, response)
  File "gae_ts_mon/config.py", line 256, in dispatch
    time_fn=time_fn)
  File "gae_ts_mon/config.py", line 218, in _instrumented_dispatcher
    ret = dispatcher(request, response)
  File "third_party/webapp2-2.5.2/webapp2.py", line 1278, in default_dispatcher
    return route.handler_adapter(request, response)
  File "third_party/webapp2-2.5.2/webapp2.py", line 1102, in __call__
    return handler.dispatch()
  File "components/auth/handler.py", line 193, in dispatch
    super(AuthenticatingHandler, self).dispatch()
  File "third_party/webapp2-2.5.2/webapp2.py", line 572, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "third_party/webapp2-2.5.2/webapp2.py", line 570, in dispatch
    return method(*args, **kwargs)
  File "handlers_bot.py", line 211, in get
    bot_code.get_swarming_bot_zip(server))
  File "server/bot_code.py", line 144, in get_swarming_bot_zip
    local_config.settings())
  File "server/bot_archive.py", line 419, in get_swarming_bot_zip
    root_dir, host, host_version, additionals, settings):
  File "server/bot_archive.py", line 396, in yield_swarming_bot_files
    with open(resolve_symlink(os.path.join(root_dir, item)), 'rb') as f:
IOError: [Errno 2] No such file or directory: '/base/data/home/apps/s~chromium-swarm-dev/3561-435d49c-tainted-smut.409815868790738271/swarming_bot/client/named_cache.py'

I'm reverting to a non-tained version of the app to see if this persists.

Still seeing the same error. I think it's this: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/1065527. I think server/bot_archive.py needed to be updated with the new path to named_cache.py.

https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/1069716