archive_util.make_archive() changes the value of the cwd, but if an
error is raised in "filename = func(base_name, base_dir, **kwargs)", the
cwd is not restored. This may happen if zlib is not available and causes
other ~60 tests to fail while running regrtest.py.

This trivial fix solve the problem here:

-    filename = func(base_name, base_dir, **kwargs)
-    if root_dir is not None:
-        log.debug("changing back to '%s'", save_cwd)
-        os.chdir(save_cwd)
+    try:
+        filename = func(base_name, base_dir, **kwargs)
+    finally:
+        if root_dir is not None:
+            log.debug("changing back to '%s'", save_cwd)
+            os.chdir(save_cwd)

The new test_make_archive_owner_group() test added in r75192 also needs
a @unittest.skipUnless(zlib, "Requires zlib"), otherwise dist_distutils
fails.
Since half of this test doesn't require zlib (i.e. when 'tar' is used)
it might be a good idea to split the test in two, in order to test the
'tar' archives even if 'zlib' is not available.

(Thanks to R. David Murray - he spot the right place where the cwd is
changed and not restored.)

I see two distinct points (besides test_make_archive_owner_group):

1- having a try..finally when changing the current working dir (I'll do
this thanks for the patch)

2- dealing with calls made on archive_util.make_archive() when zlib is
not available. What error do you get ? CompressionError I guess ?

======================================================================
ERROR: test_make_archive_owner_group
(distutils.tests.test_archive_util.ArchiveUtilTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/wolf/dev/trunk/Lib/distutils/tests/test_archive_util.py",
line 224, in test_make_archive_owner_group
    group=group)
  File "/home/wolf/dev/trunk/Lib/distutils/archive_util.py", line 237,
in make_archive
    filename = func(base_name, base_dir, **kwargs)
  File "/home/wolf/dev/trunk/Lib/distutils/archive_util.py", line 163,
in make_zipfile
    compression=zipfile.ZIP_DEFLATED)
  File "/home/wolf/dev/trunk/Lib/zipfile.py", line 675, in __init__
    "Compression requires the (missing) zlib module"
RuntimeError: Compression requires the (missing) zlib module

Done in r75659, r75662 and r75663 (merge in 2.6 maint. waiting for 2.6.4
final tag to be done)

Thanks !