Fix plugins install not returning correct exit code on failure

[arm4b]

Fixes #239 by adding error exit codes where plugin installation has failed.

[arm4b]

Looks like the fail_fast is not really implemented, but it's outside of this PR.

[PhillypHenning]

The BitOps configuration for fast_fail is implemented, it's more that it's not respected throughout the source (yet). This is something that will be worked on for 2.0.1

[arm4b]

If we're going to release v2.0.0 that advertises fail_fast functionality (yaml setting, docs https://github.com/bitovi/bitops/blob/plugins/docs/plugins.md#bitopsconfigyaml), but the feature doesn't work yet, - it perhaps better to remove/hide it for now until the full implementation.

How about removing it just from the docs temporarily so it doesn't break the expectations?

[PhillypHenning]

What's here is fine for 2.0.0, however, for 2.0.1 we will be looking to update all error messages to use the documentation.json + doc lookup functionality.

This will keep a consistent and maintainable pattern for error messages and codes.

Example;

Utilities.py (Today)

except git.exc.GitCommandError as exc:
                logger.error("\n~#~#~#~CLONING PLUGIN [{plugin_config}] FAILED~#~#~#~\n\t{stderr}"
                    .format(
                        plugin_config=plugin_config,
                        stderr=exc
                    ))
                sys.exit(1) <-- FINE FOR TODAY

Utilities.py (Tomorrow)

from doc import Get_Doc

except git.exc.GitCommandError as exc:
                logger.error("\n~#~#~#~CLONING PLUGIN [{plugin_config}] FAILED~#~#~#~\n\t{stderr}"
                    .format(
                        plugin_config=plugin_config,
                        stderr=exc
                    ))
                sys.exit( Get_Doc("git_clone_error") ) <-- Intention of tomorrow

Documentation.json

{
    "missing_plugin_dependency": {
        "msg": "Missing plugin dependency. To Fix this update the bitops/bitops.config.yaml file by adding the dependent into the bitops.plugins block.",
        "link": ""
    },
    "github_clone_error" : {
        "msg": "Github repo failed to clone",
         "link": "url-to-doc"
         "code": "501"
}

[arm4b]

The possible range for exit codes is between 0 and 255, https://unix.stackexchange.com/questions/418784/what-is-the-min-and-max-values-of-exit-codes-in-linux

The question would be how much value it can provide for the users to have a unique code for each error and the overhead for us keeping that in a dedicated .json. How many would really care if the plugin install failed with 130 or 140 and how many will lookup that in the docs when the message was already printed to them?

Could be a topic for another discussion, but I would focus on success vs failure for now.

[arm4b]

We can follow some known codes and conventions where possible though, check: https://stackoverflow.com/a/1101969/4533625

[PhillypHenning]

The BitOps configuration for fast_fail is implemented, it's more that it's not respected throughout the source (yet). This is something that will be worked on for 2.0.1