Merge pull request #2173 from ggouaillardet/topic/v2.x/travis_brew

v2.x: travis: cope with brew upgrade failure

.travis.yml

@@ -56,8 +56,8 @@ before_install:
     - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then git clone https://github.com/ofiwg/libfabric.git ; fi
     - if [[ "$TRAVIS_OS_NAME" == "linux" ]] && [[ "$GCC_VERSION" == "6" ]] ; then sudo apt-get --assume-yes install gcc-6 g++-6 gfortran-6; fi
     - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then cd libfabric && ./autogen.sh && ./configure --prefix=$HOME/bogus --enable-usnic --disable-verbs $COMPILERS && make install && cd .. ; fi
-    - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; brew upgrade automake libtool; fi
-    - if [[ "$TRAVIS_OS_NAME" == "osx" ]] && [[ "$GCC_VERSION" == "6" ]] ; then brew upgrade gcc; fi
+    - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; brew upgrade automake || true; brew upgrade libtool || true; fi
+    - if [[ "$TRAVIS_OS_NAME" == "osx" ]] && [[ "$GCC_VERSION" == "6" ]] ; then brew install gcc || true; brew upgrade gcc || true ; fi
     - mkdir -p $HOME/bogus/include $HOME/bogus/lib
 
 # Note that we use "make -k" to do the entire build, even if there was a