fix OSX travis CI

Minor tweaks to fix OSX ci. Also test out python 2.7 in addition to 3.7.

.travis.yml

@@ -8,7 +8,13 @@ matrix:
   - os: linux
     env: PYTHON=3
   - os: osx
-    env: PYTHON=3.6
+    env: PYTHON=3
+    osx_image: xcode9.3
+    python: 3.7.0
+  - os: osx
+    env: PYTHON=2
+    osx_image: xcode9.3
+    python: 2.7.14
   allow_failures:
   - os: osx
 
@@ -29,17 +35,27 @@ addons:
 
 before_install:
 - |
-  if [ "$TRAVIS_OS_NAME" = "linux" ]; then export CXX=g++-4.8 CC=gcc-4.8; fi
-  if [ "$TRAVIS_OS_NAME" = "osx" ] && [ "${PYTHON:0:1}" = "3" ]; then
-      brew update
-      brew upgrade python
-      command curl -sSL https://rvm.io/mpapis.asc | gpg --import -;
-      rvm get stable
-  else
+  PIP=pip
+  PY=python
+  if [ "$TRAVIS_OS_NAME" = "linux" ]; then 
+    export CXX=g++-4.8 CC=gcc-4.8; 
     pip install --user --upgrade pip virtualenv
     virtualenv -p python$PYTHON venv
     source venv/bin/activate
-  fi 
+  fi
+
+  if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then
+    brew update
+    brew install gcc
+    PIP=pip2
+    PY=python2
+    if  [ "${PYTHON:0:1}" = "3" ]; then
+      brew upgrade python
+      brew install python3
+      PIP=pip3
+      PY=python3
+    fi
+  fi
 
 install:
 - |
@@ -49,10 +65,12 @@ install:
     cmake similarity_search
   fi
   make -j 4
-  travis_wait travis_retry pip install -r python_bindings/requirements.txt scipy six flake8
-  travis_retry cd python_bindings && python setup.py build install && cd ..
+  travis_wait travis_retry $PIP install -r python_bindings/requirements.txt scipy six flake8
+  travis_retry cd python_bindings && $PY setup.py build install && cd ..
 
 script:
+- $PY --version
+- cd python_bindings && $PY setup.py test && flake8 && cd ..
 - |
   set -e
   if [ "$TRAVIS_OS_NAME" = "linux" -o "$TRAVIS_OS_NAME" = "osx" ] ; then
@@ -61,10 +79,6 @@ script:
       ./release/test_integr integr.log 
       cd ..
   fi
-  cd python_bindings
-  python setup.py test
-  flake8
-  cd ..
 
 cache:
   - apt