'Generic query error.
Args:
error_message: string to emit as part of the \'Parse Error\' string.
Raises:
BadQueryError and passes on an error message from the caller. Will raise
BadQueryError on all calls to __Error()'

def __Error(self, error_message):

    if (self.__next_symbol >= len(self.__symbols)):
        raise datastore_errors.BadQueryError(('Parse    Error:    %s    at    end    of    string' % error_message))
    else:
        raise datastore_errors.BadQueryError(('Parse    Error:    %s    at    symbol    %s' % (error_message, self.__symbols[self.__next_symbol])))
