Fix import based feature detection With demandimport, the following: from mercurial.util import canonpath creates an 'unloaded module' if canonpath is not a mercurial.util attribute, instead of raising AttributeError or ImportError, which defeats tests like: try: from mercurial.util import canonpath except (AttributeError, ImportError): from mercurial.scmutil import canonpath Instead, we reference the attribute explicitely, making either the modules to load or to fail loading.