The update ui had to deliver additional update messages.
Attention from design will be needed as we had to add some additional labels in case of multiple errors:
* if we can't even check if an update is available (like no network connection), we show display the error message where "Checking for update…" was displayed with a "Retry" button.
<https://wiki.ubuntu.com/SoftwareUpdates#presenting-mobile>: "* “Connect to the Internet to check for updates.”, automatically retrying a manual check if an Internet connection begins before leaving the screen; * “The update server is not responding. Try again later.” ... (There is no need for a “Retry” button, in the first case because the check will happen automatically when the problem is fixed, and in the others because the check will happen automatically when you return to the Updates screen and it’s probably a bad idea to try sooner.)"
* If we can't get any estimate for the download time from the message, the "About x seconds remaining" become: "No estimate for the download"
<https://wiki.ubuntu.com/SoftwareUpdates#presenting-mobile>: "(Time remaining should not be shown, because it is too unpredictable on mobile connections.)"
* The following items are presented in the same spot than the "Download failed:" case:
** If we can't pause a download, the message is:
"Pause failed": as primary message and then the reason delivered by the daemon as a secondary message
<https://wiki.ubuntu.com/SoftwareUpdates#presenting-mobile>: "“Pause” for a download (automatic or manual) or installation in progress, insensitive if it is no longer pauseable (and reporting a RecoverableError if it should have been)"
** If we can't install and reboot, the message is:
"Apply update failed:" as primary message and then the reason delivered by the daemon as a secondary message
<https://wiki.ubuntu.com/SoftwareUpdates#phone-progress>: "If installation fails, an alert should appear, with title “Installation Failed”, text depending on the error, and an “OK” button that returns to the update listing."
** If we can't contact the daemon for any reason, those error messages become (depending on the case):
"Can't apply the current update (can't contact service)" when clicking on install & reboot
<https://wiki.ubuntu.com/SoftwareUpdates#phone-progress>: "If installation fails, an alert should appear, with title “Installation Failed”, text depending on the error, and an “OK” button that returns to the update listing."
"Can't cancel current request (can't contact service)" when retrying from scratch an update
"Can't pause current request (can't contact service)" when pausing a download
<https://wiki.ubuntu.com/SoftwareUpdates#presenting-mobile>: "“Pause” for a download (automatic or manual) or installation in progress, insensitive if it is no longer pauseable (and reporting a RecoverableError if it should have been)"
See also bug 1282499, about how these error messages are presented.
it would also be good to specify the UI layout (if an update fails to be applied, should the user be sent back to the list of updates with a "retry" button?) where should the error message be displayed?