'Return all unique package names in all repositories.'

def all_package_names(self):

    if (self._all_package_names is None):
        all_pkgs = set()
        for repo in self.repos:
            for name in repo.all_package_names():
                all_pkgs.add(name)
        self._all_package_names = sorted(all_pkgs, key=(lambda n: n.lower()))
    return self._all_package_names
