One team I used to work on had a really healthy way of dealing with this. Whenever a bug made it through to production, the team would have an informal post-mor

One team I used to work on had a really healthy way of dealing with this. Whenever a bug made it through to production, the team would have an informal post-mortem meeting where everyone who worked on the change in question would talk about the cause of the bug, and perhaps try to identify ways something like that could have been avoided. There was no real interest in assigning blame to individuals. I think that was largely because we required two reviewers to approve every code review. So, when something did happen, it had to make it past at least three people. That automatically makes the mistake a team responsibility and not an individual one.