[MERGE][#248895] ``bzr ignore`` has better error message when versioned files match ignore pattern

[Bundle Buggy]

Bundle Buggy has detected this merge request.

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C87k56y5apj.fsf%40xemacs.org%3E
Project: Bazaar