Problems syncing images are misrepresented in UI

[Gavin Panella]

ImagesView.__init__ contains:

        try:
            sources, releases, arches = \
                get_os_info_from_boot_sources('ubuntu')
            self.connection_error = False
            self.ubuntu_sources = sources
            self.ubuntu_releases = releases
            self.ubuntu_arches = arches
        except ConnectionError:
            self.connection_error = True
            self.ubuntu_sources = []
            self.ubuntu_releases = set()
            self.ubuntu_arches = set()

However, get_os_info_from_boot_sources() consults the database, and does
no other IO. I assume it once did raise ConnectionError, but that is no
longer the case.

HOWEVER.

This has caused a different bug.

When the mechanism that populates image information hits problems, this
is not signalled to the user.

For example, a user's proxy was blocking access to maas.ubuntu.com so no
images were discovered.

The only message they were shown in the UI was:

  Error: No boot sources provide Ubuntu images.

This is only a symptom, and as such is misleading.

The only message in the logs was:

  maas.import-images: [WARNING] I/O error while syncing boot images. If
  this problem persists, verify network connectivity and disk usage.

Ideally the latter message would have also been shown in the UI. In
addition, it would be useful if the nature of the I/O error were
displayed (e.g. access denied).

[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 date of this bug report, we are marking this bug report as invalid. If you believe this is still an issue, please re-open this bug report.

Thanks