Replace getacl with du to check for files existence.

We don't currently have permissions to getacl all items in GS buckets.
However, if we can read it we can see how big it is.

BUG=chromium:285580
TEST=Ran it locally with paygen_au_canary_suite (scheduled via autotest
cli).

Change-Id: I95e743dfd2aea37f993605f6f87b359d0ff1e4cc
Reviewed-on: https://chromium-review.googlesource.com/168501
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Queue: Chris Sosa <sosa@chromium.org>
Tested-by: Chris Sosa <sosa@chromium.org>
diff --git a/gsutil_util.py b/gsutil_util.py
index 78806aa..fe66dee 100644
--- a/gsutil_util.py
+++ b/gsutil_util.py
@@ -110,7 +110,7 @@
     err_str: String to display in the error message on error.
     timeout: how long are we allowed to keep trying.
     delay: how long to wait between attempts.
-    is_regex_pattern: Whether the pattern is a regex (default: glob).
+    is_regex_pattern: Whether the pattern is a regex (otherwise a glob).
   Returns:
     The list of artifacts matching the pattern in Google Storage bucket or None
     if not found.
@@ -124,10 +124,10 @@
   # of success, or None if the actual command output should be used.
   get_methods = []
   # If the pattern is a glob and contains no wildcards, we'll first attempt to
-  # stat the file via getacl.
+  # stat the file via du.
   if not (is_regex_pattern or _GlobHasWildcards(pattern)):
-    get_methods.append(('gsutil getacl %s/%s' % (archive_url, pattern),
-                        'Failed to getacl on the artifact file.',
+    get_methods.append(('gsutil du %s/%s' % (archive_url, pattern),
+                        'Failed to du on the artifact file.',
                         pattern))
 
   # The default method is to check the manifest file in the archive directory.