Change icon on error log download
Change icon on error log download

Since saving the error log now can fail, we should give some feedback to
the user. Change the "download" icon to a "checkmark" when opening the
log, or change it to an "invalid" symbol if writing the log failed.

https://phabricator.endlessm.com/T15041

endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib