Establish LDAP connection.

def connection(self):  # pragma: no cover
        """Establish LDAP connection."""
        # self.server allows us to fetch server info
        # (including LDAP schema list) if we wish to
        # add this feature later
        self.server = ldap3.Server(self.host, port=self.port, get_info=ldap3.ALL)
        self.conn = ldap3.Connection(
            self.server,
            user=self.user_dn,
            password=self.user_pw,
            auto_bind=True,
            lazy=True,
            receive_timeout=1)