Returns a scrubbed environment variable key, PULUMI_CONFIG_<k>, that can be used for
    setting explicit varaibles.  This is unlike PULUMI_CONFIG which is just a JSON-serialized bag.

def get_config_env_key(k: str) -> str:
    """
    Returns a scrubbed environment variable key, PULUMI_CONFIG_<k>, that can be used for
    setting explicit varaibles.  This is unlike PULUMI_CONFIG which is just a JSON-serialized bag.
    """
    env_key = ''
    for c in k:
        if c == '_' or 'A' <= c <= 'Z' or '0' <= c <= '9':
            env_key += c
        elif 'a' <= c <= 'z':
            env_key += c.upper()
        else:
            env_key += '_'
    return 'PULUMI_CONFIG_%s' % env_key