Mercurial 1.7 also introduced a repository change, the dotencode requirement. This means any repository created after November 2010 with 1.7 and dotencode will not be accessible by the Mercurial from the Ubuntu LTS. This error should be familiar:
abort: requirement 'dotencode' not supported!
One solution is to use the Mercurial PPA to get a newer release.
But, it doesn't make sense to use an LTS if you are going to use software from PPAs, no?
With sun-jdk being pruned from the repositories, I'm starting to get annoyed by Ubuntu. I'm starting more and more to manage dependencies by hand instead of relying on the system. Which, imho, means the system is broken.