WebThings Gateway 1.1 reporting new version available but can't upgrade

[benfrancis]

Reported in https://discourse.mozilla.org/t/version-1-1-0/146901, I have not yet tried to reproduce, but...

STR:

• Install WebThings Gateway 1.1 Raspbian-based OS image
• Settings -> Updates

Expected:

• No new version available

Actual:

• Reports new version available, but can't be installed

This may because the update proxy is seeing the 2.0.0 release on GitHub, but there are no assets to download. It is not currently possible to automatically upgrade the WebThings Gateway 1.1 Raspbian-based OS image to 2.0.

May require a 1.1.1 bugfix release to fix.

[benfrancis]

See also: #3248