Write entry_points.txt.

def _write_entry_points(self, fp):
        """
        Write entry_points.txt.
        """
        entry_points = self.convert_entry_points()

        for group_name in sorted(entry_points):
            fp.write("[{}]\n".format(group_name))
            for ep in sorted(entry_points[group_name]):
                fp.write(ep.replace(" ", "") + "\n")

            fp.write("\n")