BUG: Fix bug in CI where failure during homebrew update occured.

Author: hjmjohnson

.travis.yml

@@ -31,7 +31,7 @@ matrix:
       osx_image: xcode9.4
       compiler: clang
       #env: PYENV_ROOT=/usr/local/var/pyenv
-      env: LIB_TYPE=static BUILD_TYPE=release
+      env: LIB_TYPE=static BUILD_TYPE=release HOMEBREW_LOGS=~/homebrew-logs HOMEBREW_TEMP=~/homebrew-temp
       #- LIB_TYPE=shared BUILD_TYPE=debug
     - os: linux
       dist: trusty