Moving to Travis stages because python various virtualenv were not be…

…ing run with the correct python version - pin virtualenv to be <20.0.0 because of pypa/virtualenv#1551 - use different distro for py37 tests

.travis.yml

@@ -5,20 +5,46 @@ dist: trusty
 services:
   - docker
 
-language: scala
-scala:
-  - 2.11.8
 
-python:
-  - "2.7"
-  - "3.6"
-  - "3.7"
-
-install:
-    -   pip install --user tox
-script:
-  - travis/travis.sh
-  - tox -c python/tox.ini -e $(echo py$TRAVIS_PYTHON_VERSION | tr -d .) -v
+jobs:
+  include:
+    - stage: "Mleap tests"
+      name: "Scala Tests"
+      language: scala
+      scala:
+        - 2.11.8
+      script:
+        - travis/travis.sh
+    - 
+      name: "Python 2.7 tests"
+      install:
+        - pip install "virtualenv<20.0.0" tox
+      language: python
+      python: 2.7
+      script:
+        - sbt +compile
+        - tox -c python/tox.ini -e py27 -v
+    - 
+      name: "Python 3.6 tests"
+      install:
+        - pip install "virtualenv<20.0.0" tox
+      language: python
+      python: 3.6
+      script:
+        - sbt +compile
+        - tox -c python/tox.ini -e py36 -v
+    - 
+      name: "Python 3.7 tests"
+      install:
+        - pip install "virtualenv<20.0.0" tox
+      language: python
+      python: 3.7
+      jdk: openjdk8  # sbt +compile fails on jdk11
+      dist: xenial  # Travis won't install py37 on trusty
+      script:
+        - echo $JAVA_HOME
+        - sbt +compile
+        - tox -c python/tox.ini -e py37 -v
 
 notifications:
   on_success: change