Improve example request_review_post_sync hook

Improve example request_review_post_sync hook so that it handles a
failure case better and so that it lets the user know more about what is
going on.

<!-- ps-id: 366f0ee9-4d8c-4c0e-9638-80137fa3883c -->

Signed-off-by: Drew De Ponte <[email protected]>

example_hooks/request_review_post_sync-github-cli-example

@@ -21,9 +21,16 @@ patch_stack_upstream_remote_url=$4 # string of the patch stack's remote url
 
 gh pr -R "$patch_stack_upstream_remote_url" view $patch_upstream_branch_name
 if [ $? -eq 0 ]; then
+  echo "gh pr -R \"$patch_stack_upstream_remote_url\" view $patch_upstream_branch_name succeded"
+
   closed=$(gh pr -R "$patch_stack_upstream_remote_url" view $patch_upstream_branch_name --json closed --jq '.closed')
-  if [ $closed != "true" ]; then
-    exit 0
+  if [ $? -eq 0 ]; then
+    echo "gh pr -R \"$patch_stack_upstream_remote_url\" view $patch_upstream_branch_name --json closed --jq '.closed' succeded"
+    echo "closed=$closed"
+    if [ $closed != "true" ]; then
+      echo "An open PR was found for the branch, so exiting to prevent duplicate PR creation."
+      exit 0
+    fi
   fi
 fi