Enforce inserting the depot_tools path as the first path in sys.path.

git-cl-upload-hook

Index: git-cl-upload-hook
diff --git a/git-cl-upload-hook b/git-cl-upload-hook
index e39fc26ee7ad61cc692272c4eedd844804aadb31..f8d860258680ce9cb3b76e2c0f5fe87125b5b5dd 100755
--- a/git-cl-upload-hook
+++ b/git-cl-upload-hook
@@ -28,7 +28,7 @@ if not depot_tools_path:
 # If we found depot_tools, add it to the script's import path.
 # Use realpath to normalize the actual path
 if depot_tools_path:
-  sys.path.append(os.path.realpath(depot_tools_path))
+  sys.path.insert(0, os.path.realpath(depot_tools_path))
 else:
   print "ERROR: Could not find depot_tools in your PATH."
   print "ERROR: Please add it to your PATH and try again."