Catch push credentials error and retry auth with reauth

[rsyring]

I was recently trying to deploy with mu and ran into problems with two different projects where the docker login before push would seemingly work but then the push would fail. Workaround: rm ~/.docker/config.json

I believe the root cause is described here. TL;DR: docker uses previously cached credentials even when logging in with new ones. This is apparently a feature not a bug.

The docker library we use offers a reauth option for .login() which probably resolves this error when it occurs. I wasn't able to test because I deleted the docker config and that resolve my problems.

I think we could try the push first, catch exceptions, if auth related, do a reauth login, and then push again. That would save the ecr.get_authorization_token() on every push and only fetch it when needed.