Guard shutil._make_archive against a logger=None argument.

Backporting two lines from the 3.x tests was enough to trigger the bug.
I also took the opportunity of making the logging call lazy.

Lib/shutil.py

@@ -359,7 +359,8 @@ def _make_tarball(base_name, base_dir, compress="gzip", verbose=0, dry_run=0,
     archive_dir = os.path.dirname(archive_name)
 
     if not os.path.exists(archive_dir):
-        logger.info("creating %s" % archive_dir)
+        if logger is not None:
+            logger.info("creating %s", archive_dir)
         if not dry_run:
             os.makedirs(archive_dir)
 

Lib/test/test_shutil.py

@@ -349,6 +349,8 @@ class TestShutil(unittest.TestCase):
         self.write_file([tmpdir, 'sub', 'file3'], 'xxx')
 
         tmpdir2 = self.mkdtemp()
+        # force shutil to create the directory
+        os.rmdir(tmpdir2)
         unittest.skipUnless(splitdrive(tmpdir)[0] == splitdrive(tmpdir2)[0],
                             "source and target should be on same drive")
 
@@ -464,6 +466,8 @@ class TestShutil(unittest.TestCase):
         self.write_file([tmpdir, 'file2'], 'xxx')
 
         tmpdir2 = self.mkdtemp()
+        # force shutil to create the directory
+        os.rmdir(tmpdir2)
         base_name = os.path.join(tmpdir2, 'archive')
         _make_zipfile(base_name, tmpdir)
 

Misc/NEWS

@@ -40,6 +40,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #9173: Let shutil._make_archive work if the logger argument is None.
+
 - Issue #12650: Fix a race condition where a subprocess.Popen could leak
   resources (FD/zombie) when killed at the wrong time.