FilesystemController has no _start_task

[Dan Bungert]

the following was observed with the ubuntu-desktop-installer client:

2021-06-18 08:01:35,477 DEBUG root:39 start: subiquity/Filesystem/guided_GET:
2021-06-18 08:01:35,479 DEBUG root:39 finish: subiquity/Filesystem/guided_GET: SUCCESS: 500 Traceback (most recent call last):
  File "/snap/ubuntu-desktop-installer/20/...
2021-06-18 08:01:35,479 DEBUG subiquity.server.server:357 request to /storage/guided?min_size=0&wait=true crashed
Traceback (most recent call last):
  File "/snap/ubuntu-desktop-installer/20/bin/subiquity/subiquity/common/api/server.py", line 123, in handler
    result = await implementation(**args)
  File "/snap/ubuntu-desktop-installer/20/bin/subiquity/subiquity/server/controllers/filesystem.py", line 217, in guided_GET
    probe_resp = await self._probe_response(wait, GuidedStorageResponse)
  File "/snap/ubuntu-desktop-installer/20/bin/subiquity/subiquity/server/controllers/filesystem.py", line 181, in _probe_response
    await self._start_task
AttributeError: 'FilesystemController' object has no attribute '_start_task'
2021-06-18 08:01:35,480 ERROR aiohttp.server:355 Error handling request
Traceback (most recent call last):
  File "/snap/ubuntu-desktop-installer/20/usr/lib/python3/dist-packages/aiohttp/web_protocol.py", line 418, in start
    resp = await task
  File "/snap/ubuntu-desktop-installer/20/usr/lib/python3/dist-packages/aiohttp/web_app.py", line 458, in _handle
    resp = await handler(request)
  File "/snap/ubuntu-desktop-installer/20/usr/lib/python3/dist-packages/aiohttp/web_middlewares.py", line 119, in impl
    return await handler(request)
  File "/snap/ubuntu-desktop-installer/20/bin/subiquity/subiquity/server/server.py", line 364, in middleware
    ErrorReportRef, report.ref())
AttributeError: 'NoneType' object has no attribute 'ref'
2021-06-18 08:01:35,482 INFO aiohttp.access:233 [18/juin/2021:08:01:35 +0000] "GET /storage/guided?min_size=0&wait=true HTTP/1.1" 500 244 "-" "-"

[Michael Hudson-Doyle (mwhudson)]

This happened because NetworkController.start() raised an exception. The failure mode is pretty bad here, probably a failure in a start() method should crash the whole server?

Not sure what the "AttributeError: 'NoneType' object has no attribute 'ref'" stuff is about either.