In https://bugs.debian.org/1005803, Matthew Vernon reports that the library documentation for sys.excepthook doesn't mention the detail that that sys.excepthook isn't called for uncaught SystemExit exceptions, although help(sys) does mention this.

(He also mentions that help(sys.excepthook) doesn't mention this.  I think this would make less sense, since that gets the docstring of a particular implementation of an excepthook - on a given system it might not be Python's built-in version, for instance.  But adding information to the main library documentation seems reasonable.)