Read a single line of text with EOF.

def readline(self, size=None):
        """Read a single line of text with EOF."""

# TODO: Add support for Unicode.
        (line, nl) = self.__buffer.read_until_nl(self.__retrieve_data)

        if self.__sf.access_type_has_universal_nl and nl is not None:
            self.__newlines[nl] = True

        return line