dev-cmd/bump: Tell the user why we didn't bump a package

- This wording might be a bit awkward, I'm open to suggestions for
  improvements!

Library/Homebrew/dev-cmd/bump.rb

@@ -269,7 +269,15 @@ def retrieve_and_display_info_and_open_pr(formula_or_cask, name, repositories, a
     EOS
 
     return unless args.open_pr?
-    return unless new_version
+
+    unless new_version
+      puts <<~EOS
+        #{title_name} was not bumped because:
+         - it has no new versions
+         - its Repology version is not the latest release on GitHub.
+      EOS
+      return
+    end
     return if pull_requests
 
     system HOMEBREW_BREW_FILE, "bump-#{type}-pr", "--no-browse",