Trying to update a boot-source-selection when the image import is stopped returns '{'os': ['OS ubuntu with release xenial has no available images for download']}

[Brendan Donegan]

In the CI, due to some strange bugs, I updated the tests to stop the image import fully before trying to add a new boot source selection. However now when I try to do that I get:

{"os": ["OS ubuntu with release xenial has no available images for download"]}

I'm not sure how MAAS is determing that there are 'no available images for download' of xenial.

[Blake Rouse (blake-rouse)]

Updating the caching of what selections are available is a delayed process. I would say its just because you did it to fast. It shouldn't take long to update. How long are you waiting before updating the selections?

[Brendan Donegan (brendan-donegan)]

As I showed you in person, the boot source cache is empty when this occurs:

>>> from maasserver.models import BootSourceCache
>>> BootSourceCache.objects.all()
[]

There's also a bunch of tracebacks in regiond.log, like this:

2016-12-09 09:43:30 -: [critical] Unhandled error in EventualResult
        Traceback (most recent call last):
          File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 393, in callback
            self._startRunCallbacks(result)
          File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 501, in _startRunCallbacks
            self._runCallbacks()
          File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line
588, in _runCallbacks
            current.result = callback(current.result, *args, **kw)
          File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1184, in gotResult
            _inlineCallbacks(r, g, deferred)
        --- <exception caught here> ---
          File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1128, in _inlineCallbacks
            result = g.send(result)
        builtins.StopIteration:

[Andres Rodriguez (andreserl)]

Hi!

**This is an automated message**

We believe this is may no longer be an issue in the latest MAAS release. Due to the original date of the bug report, we are currently marking it as Invalid. If you believe this bug report still valid against the latest release of MAAS, or if you are still interested in this, please re-open this bug report.

Thanks