🐛 Supplying no `--config` value errors

[gvee-uk]

If you run the app without supplying a value for the --config argument (either on the command line or via environment variables) then the following exception is thrown:

\src\sql-deployment-tools.py", line 57, in <module>
    if not args.config.name.endswith(".toml"):
AttributeError: 'Namespace' object has no attribute 'config'

Note, this might be fixed as part of the work to swap from argparser (@EuanMason is working on #5), but raising the issue to track to see if the behaviour is still present then.