Ignore 404 NOT FOUND when trying to delete a tag

[spkane]

Signed-off-by: Sean P. Kane [email protected]

- What I did

Added code to log, but otherwise ignore 404 NOT FOUND errors when deleting tags.

This addresses some additional functionality that was mentioned in: https://github.com/docker/hub-tool/issues/58

- How I did it

Via a few lines of Go code

- How to verify it

Try and run a command like this twice against an existing image tag (or just run it against something that does not exist).

hub-tool tag rm -f myrepo/myimage:mytag
hub-tool tag rm -f myrepo/myimage:mytag

- Description for the changelog

• Do not throw fatal errors when trying to delete a non-existent image tag.