hginitializer now works with Mercurial 1.6. Apparently Mercurial had
an API change in version 1.6.
The workaround is rather simple:
# Mercurial <= 1.5
repo.add(['.hgignore'])
# Mercurial >= 1.6
repo[None].add(['.hgignore'])
Can be found in changeset:
http://bitbucket.org/brejoc/hginitializer/changeset/71d244687099