Always generate a comment for mypy_primer (#5197)

This way, runs without output after runs with output can be clearly
determined. This also makes it easier to recognize when a run was not
completed.

Author: srittau

.github/workflows/mypy_primer_comment.yml

@@ -89,11 +89,15 @@ jobs:
 
             console.log("Diff from mypy_primer:")
             console.log(data)
+            let body;
             if (data.trim()) {
-              await github.issues.createComment({
-                issue_number: context.issue.number,
-                owner: context.repo.owner,
-                repo: context.repo.repo,
-                body: 'Diff from [mypy_primer](https://github.com/hauntsaninja/mypy_primer), showing the effect of this PR on open source code:\n```diff\n' + data + '```'
-              })
+              body = 'Diff from [mypy_primer](https://github.com/hauntsaninja/mypy_primer), showing the effect of this PR on open source code:\n```diff\n' + data + '```'
+            } else {
+              body = 'According to [mypy_primer](https://github.com/hauntsaninja/mypy_primer), this change has no effect on the checked open source code. 🤖🎉'
             }
+            await github.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body,
+            })