platform flags

I didn't have problems using debuggers when the form was:

`FLAGS = flags.FLAGS`

and later on:

```
# Make sure the required fields are available in the config.
base_config.validate_config(FLAGS.config)
```

But I get errors with the new version:

```
# Make sure the required fields are available in the config.
config = _CONFIG.value
base_config.validate_config(config)
```

_CONFIG is None seems to be the problem. I'm using debugger from either PyCharm or VSCode.