How to use the distutils2.errors.IrrationalVersionError function in Distutils2

eggs = to_dict(args.input.read())
    nix_write = args.output.write

    nix_write(PRE_TMPL)

    not_found = []
    version_error = []
    for nixname in sorted(eggs.keys()):
        if nixname in SYSTEM_PACKAGES: continue
        if nixname in IGNORE_PACKAGES: continue
        egg = eggs[nixname]
        try:
            args.output.write(TMPL % to_nix_dict(egg, nixname))
        except ProjectNotFound:
            not_found.append(egg['name'])
        except IrrationalVersionError:
            version_error.append(egg['name'])

    nix_write(POST_TMPL)
    nix_write(
        "# Not Found: {0}\n# Version Error: {1}".format(
            not_found, version_error)
    )

for nixname in sorted(eggs.keys()):
        if nixname in system_packages: continue
        if nixname in ignore_packages: continue
        egg = eggs[nixname]
        version = suggest_normalized_version(egg['version'])
        name = egg['name']
        if egg['extras']:
            name += '-'.join(egg['extras'])
        name += '-' + egg['version']
        if version is None:
            version = ''
        try:
            egg_release = pypi.get_release(egg['name'] + '==' + egg['version'])
        except ProjectNotFound:
            not_found.append(egg['name'])
        except IrrationalVersionError:
            version_error.append(egg['name'])
        egg_dist = egg_release.dists['sdist'].url
        url = egg_dist['url']
        url = url.replace("http://a.pypi", "http://pypi")
        #metadata = nix_metadata(egg_release)
        metadata = ''
        url = url.replace(name, "${name}")
        build_inputs = ''
        if url.endswith(".zip"):
            build_inputs = "\n    buildInputs = [ pkgs.unzip ];\n"
        propagated_build_inputs = ''
        if nixname in hard_requirements.keys():
            propagated_build_inputs = (
                "\n    propagatedBuildInputs = [ {0} ];\n"
        ).format(hard_requirements[nixname])
        print TMPL % {'nixname': nixname,