@jirikuncar E901 are parsing errors during `compile`. The reason of this is Python 2.6. Anyway, the tests will eventually break.

> A partial list of 3.1 features that were backported to 2.7:
> * The syntax for set literals (`{1,2,3}` is a mutable set).
>
> http://docs.python.org/dev/whatsnew/2.7.html#python-3-1-features