Travis: Fix tools testing breakage due to multiple python versions

.travis.yml

@@ -10,7 +10,7 @@ env:
       --data @- << DATA\n{
       "state": "$0",
       "description": "$1",
-      "context": "travis-ci/$NAME/$(python --version)",
+      "context": "travis-ci/$NAME",
       "target_url": "https://travis-ci.org/$TRAVIS_REPO_SLUG/jobs/$TRAVIS_JOB_ID"
       }\nDATA'
 
@@ -74,23 +74,31 @@ matrix:
 
     - env:
         - NAME=tools
-      python:
-        - '2.7'
-        - '3.5'
-        - '3.6'
       install:
         # Install dependencies
-        - sudo apt-get install gcc-arm-embedded
-        - pip install -r requirements.txt
-        - pip install pytest pylint hypothesis mock coverage coveralls
+        - sudo add-apt-repository -y ppa:deadsnakes/ppa
+        - sudo apt-get update
+        - sudo apt-get install gcc-arm-embedded python{2.7,3.5,3.6} python{,3}-pip
+        - pip2 install -r requirements.txt
+        - pip3 install -r requirements.txt
+        - pip2 install pytest pylint hypothesis mock coverage coveralls
+        - pip3 install pytest pylint hypothesis mock coverage coveralls
         # Print versions we use
         - arm-none-eabi-gcc --version
-        - python --version
+        - python2.7 --version
+        - python3.5 --version
+        - python3.6 --version
       script:
         # Run local testing on tools
-        - PYTHONPATH=. coverage run -a -m pytest tools/test
-        - python2 tools/test/pylint.py
-        - coverage run -a tools/project.py -S | sed -n '/^Total/p'
+        - PYTHONPATH=. coverage-2.7 run -a -m pytest tools/test
+        - PYTHONPATH=. coverage-3.5 run -a -m pytest tools/test
+        - PYTHONPATH=. coverage-3.6 run -a -m pytest tools/test
+        - python2.7 tools/test/pylint.py
+        - python3.5 tools/test/pylint.py
+        - python3.6 tools/test/pylint.py
+        - coverage-2.7 run -a tools/project.py -S | sed -n '/^Total/p'
+        - coverage-3.5 run -a tools/project.py -S | sed -n '/^Total/p'
+        - coverage-3.6 run -a tools/project.py -S | sed -n '/^Total/p'
         - coverage html
       after_success:
         # Coverage for tools
@@ -199,8 +207,3 @@ matrix:
       env: NAME=mbed2-NUVOTON
     - <<: *mbed-2
       env: NAME=mbed2-RENESAS
-      # Change python version here only because 3x the other jobs does not add any more coverage
-      python:
-        - '2.7'
-        - '3.5'
-        - '3.6'