gsutil: upgrade from 4.19 to 4.27

BUG=chromium:640476
TEST='./lib/gs_unittest --network' passes
TEST='./lib/paygen/gslib_unittest --network' passes
TEST='./lib/paygen/gslock_unittest --network' passes
TEST='./lib/paygen/gspaths_unittest --network' passes

Change-Id: I4bdb25524ae8b388491894756f9445a03b9d94cb
Reviewed-on: https://chromium-review.googlesource.com/653370
Commit-Ready: Xixuan Wu <xixuan@chromium.org>
Tested-by: Xixuan Wu <xixuan@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
(cherry picked from commit 9e2f6cc0b698872b0fe7bf7863de844ded5fce63)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2348400
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/lib/gs.py b/lib/gs.py
index e844e20..b08e931 100644
--- a/lib/gs.py
+++ b/lib/gs.py
@@ -253,7 +253,7 @@
   # (1*sleep) the first time, then (2*sleep), continuing via attempt * sleep.
   DEFAULT_SLEEP_TIME = 60
 
-  GSUTIL_VERSION = '4.19'
+  GSUTIL_VERSION = '4.27'
   GSUTIL_TAR = 'gsutil_%s.tar.gz' % GSUTIL_VERSION
   GSUTIL_URL = (PUBLIC_BASE_HTTPS_URL +
                 'chromeos-mirror/gentoo/distfiles/%s' % GSUTIL_TAR)