Sysupgrade process shouldn't continue if the firmware image couldn't be downloaded. Ref: http://lists.infradead.org/pipermail/openwrt-devel/2019-December/020940.html Reported-by: Petr Novák <petrn@me.com> Signed-off-by: Petr Štetiar <ynezz@true.cz> (cherry picked from commit cf3da66d2ce11a30ae2993b56276ade10c9bddb9)