gn_helpers: move to explicit import

We want to pull third_party out of implicit sys.path search,
so change importing of this module to explicit.

BUG=b:187794934
TEST=CQ passes

Change-Id: I46bac8245fc3fafe8cd424a2986d978a8b936b00
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2896049
Tested-by: Mike Frysinger <vapier@chromium.org>
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Chris McDonald <cjmcdonald@chromium.org>
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
diff --git a/scripts/deploy_chrome.py b/scripts/deploy_chrome.py
index 7b810e8..ffdb53d 100644
--- a/scripts/deploy_chrome.py
+++ b/scripts/deploy_chrome.py
@@ -31,20 +31,20 @@
 import sys
 import time
 
-from chromite.lib import constants
-from chromite.lib import failures_lib
 from chromite.cli.cros import cros_chrome_sdk
 from chromite.lib import chrome_util
 from chromite.lib import commandline
+from chromite.lib import constants
 from chromite.lib import cros_build_lib
 from chromite.lib import cros_logging as logging
+from chromite.lib import failures_lib
 from chromite.lib import gs
 from chromite.lib import osutils
 from chromite.lib import parallel
 from chromite.lib import remote_access as remote
 from chromite.lib import retry_util
 from chromite.lib import timeout_util
-from gn_helpers import gn_helpers
+from chromite.third_party.gn_helpers import gn_helpers
 
 
 assert sys.version_info >= (3, 6), 'This module requires Python 3.6+'