docs: def _set_conn(self):
          """Establish connection to the server"""
          if self._tls:
              ldap.set_option(ldap.OPT_X_TLS_REQUIRE_CERT, ldap.OPT_X_TLS_NEVER)
          try:
              conn = ldap.initialize(self._url)
              conn.set_option(ldap.OPT_NETWORK_TIMEOUT, self._timeout)
              conn.simple_bind_s(self._binddn, self._bindpw)
          except Exception as e:
              if hasattr(e, 'message') and 'desc' in e.message:
                  msg = e.message['desc']
              else:
                  msg = e.args[0]['desc']
              log.critical(msg)
              raise
          log.debug('%s connection established' % ('LDAPS' if self._tls else 'LDAP'))
          self._conn = conn