update osx image

Author: rusty1s

.travis.yml

@@ -3,22 +3,24 @@ language: python
 jobs:
   include:
     - os: linux
-      python: 3.6
+      python: 3.7
+      before_install:
+        - export CC=gcc-5
+        - export CXX=g++-5
     - os: osx
-      python: 3.6
+      osx_image: xcode10.2
+      python: 3.7
+      before_install:
+        - export MACOSX_DEPLOYMENT_TARGET=10.9
+        - export CC=clang
+        - export CXX=clang++
 addons:
   apt:
     sources:
       - ubuntu-toolchain-r-test
     packages:
       - gcc-5
       - g++-5
-before_install:
-  - if [ "TRAVIS_OS_NAME" = "linux"]; then export CC=gcc-5; fi
-  - if [ "TRAVIS_OS_NAME" = "linux"]; then export CXX=g++-5; fi
-  - if [ "TRAVIS_OS_NAME" = "osx"]; then export MACOSX_DEPLOYMENT_TARGET=10.9; fi
-  - if [ "TRAVIS_OS_NAME" = "osx"]; then export CC=clang; fi
-  - if [ "TRAVIS_OS_NAME" = "osx"]; then export CXX=clang++; fi
 install:
   - pip install numpy
   - pip install --pre torch torchvision -f https://download.pytorch.org/whl/nightly/cpu/torch_nightly.html