When Github release assets are building we can get transient errors

[philclifford]

When Github release assets are building we either hit "latest" with no deb found, causing the

  [!] ERROR! Missing required information

until the assets appear, or we always get all releases (quite huge for some repos) and the last releases will keep being presented until the assets appear.

Originally posted by @philclifford in #1049 (comment)

[philclifford]

Possibly a general approach would be to dispense with "latest" for github entirely and just grep the .deb lines for the cache. Some repos will generate a fair amount of data over the network but this way we don't get these intermittent errors although we lose any indication that a release is in progress and some time and network costs.

Personally I prefer to keep "latest" where possible now that this error does not break updates entirely. If we keep this behaviour we should document the scenario and add a note to the error message that a release may be in progress - try again in a while