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

[Martin Pool]

Martin Pool has voted approve.
Status is now: Approved
Comment:
I'll merge it.

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C49B5754D.2050906%40wartburg.edu%3E
Project: Bazaar