Improve fail message

[petricm]

something like

git fetch upstream
git checkout upstream/rel-v7r1 -b cherry-pick-2-511b62fe5-rel-v7r1
git cherry-pick -m 1 511b62fe5
git status
# Fix the conflicts
git cherry-pick --continue
# If you have the GitHub CLI installed the PR can be made with
gh pr create \
     --label 'sweep:from rel-v7r2' \
     --base rel-v7r1 \
     --repo DIRACGrid-test/DIRAC \
     --title 'Sweeping #47 from rel-v7r2 to rel-v7r1. Optimise ClassAd.asJDL' \
     --body 'Optimise ClassAd.asJDL (#47)


Adding original author @chrisburr as watcher.'