Retrieve the first value for a section/key.

        Raises:
            KeyError: If no line match the given section/key.

def get_one(self, section, key):
        """Retrieve the first value for a section/key.

        Raises:
            KeyError: If no line match the given section/key.
        """
        lines = iter(self.get(section, key))
        try:
            return next(lines)
        except StopIteration:
            raise KeyError("Key %s not found in %s" % (key, section))