This happens for real with msgpack egg / C-library.

-> Fix handling of such situation via using (name, kind) instead of only
name as BOM key. Without the fix added test breaks as

    def addbom(urlpath, kind, version=None):
        name, ver = namever(urlpath)
        if version is not None:
            assert ver is None
            ver = version
        ver = removeprefix(ver, name+'-')   # wendelin.core-2.0.alpha3-0-g6315384  -> 2.0.alpha3-0-g6315384
        if '//' in urlpath:
            url = urlpath
        else:
            if kind == 'egg':
                # XXX not strictly correct -> better retrieve the actual URL, but buildout does not save it in installed.cfg
                url = 'https://pypi.org/project/%s/%s/' % (name, ver)
            else:
                raise NotImplementedError('TODO url for kind %r  (urlpath: %r)' % (kind, urlpath))

        info = PkgInfo(name, ver, kind, url)
        if name in bom:
>           assert bom[name] == info,  (bom[name], info)
E           AssertionError: (PkgInfo(name='msgpack', version='0.5.4', kind='', url='http://downloads.sourceforge.net/project/msgpack/msgpack/cpp/msgpack-0.5.4.tar.gz'), PkgInfo(name='msgpack', version='0.6.2', kind='egg', url='https://pypi.org/project/msgpack/0.6.2/'))