Could you not check for credHelpers on init?

[nomagick]

Request

Could you change the implementation a bit to not check for credHelpers binaries on init?

Context

We are kind of a PaaS/SaaS provider, and we are providing a credHelper for a particular registry.

However, the helper script, namely docker-credential-[the-thing], is part of a Python package.

Motivation

Contrary to the system credStore plugins, which are typically binary and installed to system PATH statically,
executables from Python packages tend to have some "Dynamicity", for example, managed by tools like pyenv or conda and have something to do with "active profile" configuration.

Now that the credHelper plugin is somewhat dynamic, the Docker configuration file, namely DOCKER_CONFIG/config.json is not expected to really change with the "active python environment" settings.

So it comes to a situation where people install our credHelper in a particular python environment and modifies the Docker configuration file to use the helper plugin. Then they move to some other python environment which does not have the helper plugin installed.

When people try to load docker-py from the environment without the plugin, it fails with docker.credentials.errors.InitializationError: docker-credential-[name-of-plugin] not installed or not available in PATH.

This kind of error does not trigger when people use the command-line docker client.

[milas]

It seems reasonable to emit a warning here instead. Any operations that require authentication will end up failing regardless.

Happy to review a PR for this.