issue2551232 - modify in-reply-to threading when multiple matches if an email is missing an issue designator, in-reply-to threading is attempted. In this change if in-reply-to threading matches multiple issues, fall back to matching on subject. It used to just arbitrairly choose the first matching issue.

from roundup.dist.command.build import build_message_files, check_manifest
from setuptools.command.install_lib import install_lib as base

class install_lib(base):

    def run(self):
        check_manifest()
        build_message_files(self)
        base.run(self)