travis-ci: use system python
travis-ci: use system python

pombredanne/stdeb,benthomasson/stdeb,astraw/stdeb,astraw/stdeb,LeMeteore/stdeb,sathieu/stdeb,pombredanne/stdeb,pombredanne/stdeb,LeMeteore/stdeb,astraw/stdeb,benthomasson/stdeb,sathieu/stdeb,LeMeteore/stdeb,benthomasson/stdeb,sathieu/stdeb