qemu-native-helper has an additional task that needs to be run in order
for testimage to work. This task is usually run by default in a full
build but there are use cases where it might be skipped. This commit
adds the dependency explicitly.
Also, this commit adds a try/catch error message to make it clearer what
you need to do if you try to run testimage before you have built or
downloaded the image artifacts.
[YOCTO #11375]
Signed-off-by: brian avery <brian.avery@intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
