I just tried to run the upgrades and I got the following:
Download failed.
The list of errors is attached. The recovery for this case is currently not implemented. If you see 404 errors, it might be useful to try fetching package lists (see the Sources tab) and retrying the operation.
The error was:
APT Error. Context:
Package download failed,
Unable to correct problems, you have held broken packages.,
Unable to correct problems, you have held broken packages.,
Unable to correct problems, you have held broken packages.,
: