Travis: Improve testing organisation

Split the tests into their own jobs so it is easier to see what test is
failing, also only run pep8 and pylint tests with python 3.6 as it is
uncessary to run with both python versions.

.travis.yml

@@ -16,20 +16,34 @@
 language: python
 
 python:
-    - "2.7"
     - "3.6"
+    - "2.7"
 
 install:
     - pip install nose
     - pip install nose2
     - pip install flake8
     - pip install pylint
-
-script:
     - git clone -v https://github.com/ARM-software/devlib.git /tmp/devlib && cd /tmp/devlib && python setup.py install
     - cd $TRAVIS_BUILD_DIR && python setup.py install
-    - nose2 -s $TRAVIS_BUILD_DIR/tests
-    - cd /tmp && wa run $TRAVIS_BUILD_DIR/tests/travis/idle_agenda.yaml -v -d idle_workload
-    - cd $TRAVIS_BUILD_DIR && ./dev_scripts/pylint wa
-    - cd $TRAVIS_BUILD_DIR && ./dev_scripts/pep8 wa
 
+env:
+    global:
+        - PYLINT="cd $TRAVIS_BUILD_DIR && ./dev_scripts/pylint wa"
+        - PEP8="cd $TRAVIS_BUILD_DIR && ./dev_scripts/pep8 wa"
+        - NOSETESTS="nose2 -s $TRAVIS_BUILD_DIR/tests"
+        - WORKLOAD="cd /tmp && wa run $TRAVIS_BUILD_DIR/tests/travis/idle_agenda.yaml -v -d idle_workload"
+    matrix:
+        - TEST=$PYLINT
+        - TEST=$PEP8
+        - TEST=$NOSETESTS
+        - TEST=$WORKLOAD
+script:
+    - echo $TEST && eval $TEST
+
+matrix:
+    exclude:
+        - python: "2.7"
+          env: TEST=$PYLINT
+        - python: "2.7"
+          env: TEST=$PEP8