The way I found to make this work is to mirror my bitbucket projects on github using hg-git. Below is an example from fastavro.
First, you need to install hg-git. It's available from PyPI, "pip install hg-git" will do the trick, (or "easy_install hg-git" if you don't have pip).
Then create a repository on github to mirror the one on bitbucket. After that tell travis-ci to watch this repository.
Next step is to enable hg-git in your repository, edit .hg/hgrc and add the following:
[extensions] hgext.bookmarks = hggit =
Then "bootstrap" it with the following command:
hg bookmark -r default master
Next step is to create .travis.yml, For fastavro I have both Python 2.7 and 3.2.
Last step, is to make sure every time we push to bitbucket, changes are pushed to github as well. This is done with an outgoing hook in .hg/hgrc
[hooks] outgoing = hg push git+ssh://email@example.com/tebeka/fastavro.git || true
(The || true is there since hg push will exit with non-zero value sometimes)
That's all. Now fastavro has continuous integration that runs both on Python 2.7 and 3.2.