I did a blame-free post-mortem of https://bugs.debian.org/858058 (aka. #11527). It happened because of the combination of a number of small failures and missing pieces:

• lack of automated QA for this feature: requested autopkgtests in Debian on https://bugs.debian.org/858204, upstream tests would be welcome as well but that's not what this ticket is about
• lack of manual QA for this feature: I'll ignore this for now, hoping that automated QA is implemented soon enough; if this doesn't happen we should probably consider documenting a manual test suite in our release process doc
• developers not testing the code they just refactored: I don't think we can do much about this, except learning from this sad experience
• menu_activate_cb in nautilus/nautilus-mat.py being overly self-confident, and thus not robust enough in face of programming errors => silently failing

This ticket is about the last of these root causes: perhaps menu_activate_cb should wrap all its code in a try/catch block, and display an error dialog to the user if any unhandled exception is raised.

Thoughts?