Merge pull request #2155 from peastman/travis

Fix Travis error on Mac

.travis.yml

@@ -109,9 +109,10 @@ before_install:
   - wget http://anaconda.org/omnia/ccache/3.2.4/download/${TRAVIS_OS_NAME}-64/ccache-3.2.4-0.tar.bz2
   - mkdir -p $HOME/ccache && tar xf ccache-3.2.4-0.tar.bz2 -C $HOME/ccache
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then
+      brew cask uninstall oclint;
       brew install fftw;
       brew install -y https://raw.githubusercontent.com/Homebrew/homebrew-core/5b680fb58fedfb00cd07a7f69f5a621bb9240f3b/Formula/doxygen.rb;
-      sudo easy_install pytest;
+      sudo pip install -U pytest --ignore-installed six;
     fi
   - if [[ "${TRAVIS_OS_NAME}" == "linux" ]]; then
       CMAKE_URL="http://cmake.org/files/v3.7/cmake-3.7.2-Linux-x86_64.tar.gz";