Building images fails on auth errors even when auth is not required

[rsmith49]

The Problem

When running DockerClient.images.build(...), if a StoreError is raised when running AuthConfig._resolve_authconfig_credstore (link) when trying to create auth headers for the build request, the whole command fails.

For my specific example, I have gcloud auth artifacts on my local machine that require login once per day - if I have not logged in and try to build a publicly accessible image, that build will still fail since docker-credentials-gcloud get exits non-zero by prompting me to log in again, even though that auth is not required.

Proposed Solution

Either:

• try/except each call to _resolve_authconfig_credstore in get_all_credentials (link and link) and just don't add them to auth_data if the call errors
• do not raise a DockerExecption from the StoreError in _resolve_authconfig_credstore and treat it the same as a CredentialsNotFound error (I could see this breaking other things)