Provide generic message on failure

Author: susodapop

.github/workflows/dco-check.yml

@@ -18,5 +18,6 @@ jobs:
               issue_number: context.issue.number,
               owner: context.repo.owner,
               repo: context.repo.repo,
-              body: "${{ steps.run_tests.error }}"
+              body: `Thanks for your contribution! To satisfy the DCO policy in our [contributing guide](CONTRIBUTING.md)
+              every commit message must include a sign-off. You can retroactively apply this sign-off with an interactive rebase.`
             })