Hey,

> If we really want to capture the output of ‘guix system init’, then we
> need to open a pseudo-terminal with ‘openpty’ & co. instead of ‘pipe’ in
> ‘run-external-command-with-handler’.  That may be relatively easy
> actually.

So I implemented your proposal. It seems to be working quite well. As
discussed on #guix, we could avoid to dump the download bars to the
syslog if the "guix system init" command succeeds. However, it seems
quite tricky in the current implementation where the syslog dumping is
actually a hook (%syslog-line-hook).

Fixing this issue, I also realized that when the "guix system init"
command fails, the user is only offered to resume the installation or
restart it.

In cases where "guix system init" failed because of a network issue, or
because a partition was too small, restarting/resuming seems like the
right thing to do.

However, when the installer failed because "guix system init" crashed or
segfaulted, restarting/resuming won't probably help, and dumping the
crash is probably the best way to get help. That's why I added in a
second patch, a new button "Report the failure" to the
"run-install-failed-page".

Thanks,

Mathieu