Comment 1 for bug 954663

I don't think this is only a problem in bzr-externals, unfortunately, because on a Precise installation containing

 ii bzr 2.5.0-2ubuntu2 easy to use distributed version control system
ii bzr-fastimport 0.13.0-1 Fast-import/fast-export plugin for Bazaar
ii bzrtools 2.5-1 Collection of tools for bzr
ii python-bzrlib 2.5.0-2ubuntu2 distributed version control system - python library

I am still seeing this issue (and I don't seem to even have an externals.py file on my filesystem).