def _ensure_pgrp(self):
        """Ensures that the pgrp file is present and up to date. There have
        been production cases where the file was lost or not
        immediately emitted due to disk space issues.
        """
        if not LAST_PGRP_PATH:  # global
            return
        try:
            with open(LAST_PGRP_PATH, 'w') as f:
                f.write(str(os.getpgrp()) + "\n")
        except IOError:
            # raised if no permissions or disk space
            pass
Ensures that the pgrp file is present and up to date. There have
        been production cases where the file was lost or not
        immediately emitted due to disk space issues.