return the contents of pg_controldata, or non-True value if pg_controldata call failed

def controldata(self):
        """ return the contents of pg_controldata, or non-True value if pg_controldata call failed """
        result = {}
        # Don't try to call pg_controldata during backup restore
        if self._version_file_exists() and self.state != 'creating replica':
            try:
                env = {'LANG': 'C', 'LC_ALL': 'C', 'PATH': os.getenv('PATH')}
                if os.getenv('SYSTEMROOT') is not None:
                    env['SYSTEMROOT'] = os.getenv('SYSTEMROOT')
                data = subprocess.check_output([self._pgcommand('pg_controldata'), self._data_dir], env=env)
                if data:
                    data = data.decode('utf-8').splitlines()
                    # pg_controldata output depends on major verion. Some of parameters are prefixed by 'Current '
                    result = {l.split(':')[0].replace('Current ', '', 1): l.split(':', 1)[1].strip() for l in data
                              if l and ':' in l}
            except subprocess.CalledProcessError:
                logger.exception("Error when calling pg_controldata")
        return result