Fix distutil test

https://travis-ci.org/serge-sans-paille/pythran/jobs/35088901
As disutils fails on the original contruct, I though it was because you write : `python -c "import demo"` (in shell) and not `python -c import demo`.
I can't reproduce this issue on my computer so I push this PR to test if it is the solution. If it is not, you can close it.