bpo-34661: Fix test skipping call. (GH-9266)

(cherry picked from commit e78734d579439861f6d7e12f35d268836b2c1e24)

Co-authored-by: Benjamin Peterson <benjamin@python.org>
diff --git a/Lib/test/test_shutil.py b/Lib/test/test_shutil.py
index ee23ac8..6e2b100 100644
--- a/Lib/test/test_shutil.py
+++ b/Lib/test/test_shutil.py
@@ -1125,7 +1125,7 @@
             except subprocess.CalledProcessError as exc:
                 details = exc.output.decode(errors="replace")
                 if 'unrecognized option: t' in details:
-                    self.skip("unzip doesn't support -t")
+                    self.skipTest("unzip doesn't support -t")
                 msg = "{}\n\n**Unzip Output**\n{}"
                 self.fail(msg.format(exc, details))