Lookup a future contract by symbol.

        Parameters
        ----------
        symbol : str
            The symbol of the desired contract.

        Returns
        -------
        future : Future
            The future contract referenced by ``symbol``.

        Raises
        ------
        SymbolNotFound
            Raised when no contract named 'symbol' is found.

def lookup_future_symbol(self, symbol):
        """Lookup a future contract by symbol.

        Parameters
        ----------
        symbol : str
            The symbol of the desired contract.

        Returns
        -------
        future : Future
            The future contract referenced by ``symbol``.

        Raises
        ------
        SymbolNotFound
            Raised when no contract named 'symbol' is found.

        """

        data = self._select_asset_by_symbol(self.futures_contracts, symbol)\
                   .execute().fetchone()

        # If no data found, raise an exception
        if not data:
            raise SymbolNotFound(symbol=symbol)
        return self.retrieve_asset(data['sid'])