Convert a package's long description to HTML.

def render_long_description(self, dirname):
        """Convert a package's long description to HTML.
        """
        with changedir(dirname):
            self.setuptools.check_valid_package()
            long_description = self.setuptools.get_long_description()
            outfile = abspath('.long-description.html')
            self.docutils.publish_string(long_description, outfile, self.styles)
            return outfile