another attempt at a matrix build for OS X platform CI testing, modifies python install relative to build phase

.travis.yml

@@ -1,5 +1,5 @@
 sudo: true
-language: python
+language: generic
 
 env:
   - TARGET="lint"
@@ -13,15 +13,20 @@ matrix:
         - pip install ufolint
         - sudo apt-get -qq update
         - sudo apt-get install -y shellcheck
+      script:
+        - make -j $TARGET
     - os: osx
-      before_script:
+      before_install:
         - brew update
-        - brew install python
-        - pip install shellcheck
+        - brew install python3
+        - virtualenv env -p python3
+        - source env/bin/activate
+      before_script:
+        - pip install ufolint
         - brew outdated shellcheck || brew upgrade shellcheck
+      script:
+        - make -j $TARGET
 
-script:
-  - make -j $TARGET
 
 notifications:
   email: false