Enforce basic pep8 checking

.travis.yml

@@ -1,4 +1,10 @@
-language: cpp
+language:
+  - cpp
+  - python
+
+python:
+  - 3.5
+
 sudo: required
 
 services:
@@ -10,6 +16,8 @@ notifications:
 
 install:
   - docker build -t calamares .
+  - pip install pep8
 
 script:
   - docker run -v $PWD:/build calamares bash -lc "cd /build && cmake -DWEBVIEW_FORCE_WEBKIT=1 -DKDE_INSTALL_USE_QT_SYS_PATHS=ON . && make -j2"
+  - pep8 $PWD