Parse out ssl_options for Cassandra cluster connection.
    Make sure that the ssl_version (if any specified) is valid.

def _get_ssl_opts():
    '''
    Parse out ssl_options for Cassandra cluster connection.
    Make sure that the ssl_version (if any specified) is valid.
    '''
    sslopts = __salt__['config.option']('cassandra').get('ssl_options', None)
    ssl_opts = {}

    if sslopts:
        ssl_opts['ca_certs'] = sslopts['ca_certs']
        if SSL_VERSION in sslopts:
            if not sslopts[SSL_VERSION].startswith('PROTOCOL_'):
                valid_opts = ', '.join(
                    [x for x in dir(ssl) if x.startswith('PROTOCOL_')]
                )
                raise CommandExecutionError('Invalid protocol_version '
                                            'specified! '
                                            'Please make sure '
                                            'that the ssl protocol'
                                            'version is one from the SSL'
                                            'module. '
                                            'Valid options are '
                                            '{0}'.format(valid_opts))
            else:
                ssl_opts[SSL_VERSION] = \
                    getattr(ssl, sslopts[SSL_VERSION])
        return ssl_opts
    else:
        return None