Image push/pull failure check

[lnovara]

It would be nice to add some form of reporting at the end of the sync to signal which images failed the pull/push stage in order to give feedback to the user for further investigations.

[nutellinoit]

First idea 💡 :

• check the exit code from the pull and push stage, add all the failures on a txt files
• send a webhook to slack with the failures

[lnovara]

Honestly I would start simple with just having the pipeline fail if at least one image was not pulled/pushed correctly and giving feedback to the user in the pipeline output.

[lnovara]

Addendum: if the pull from upstream fails the scripts output that no sync is needed which is a bit misleading.