fix travis tests

.travis-before_install.sh

@@ -27,11 +27,8 @@ if [ "$Compiler_version" != "" ] && [ "$Compiler_version" != "default" ]; then
   fi
   set -x
   if [ "$VersionAvByDefault" = "" ]; then
-    if [ "$Compiler_name" = "gcc" ]; then
-
-      # ubuntu test toolchain needed for more recent version of gcc
-      sudo add-apt-repository --yes "deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu ${codename} main"
-    fi
+    # ubuntu test toolchain needed for more recent version of gcc and clang-6.0
+    sudo add-apt-repository --yes "deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu ${codename} main"
   fi
 fi
 
@@ -53,12 +50,11 @@ if [ "$Compiler_version" != "" ] && [ "$Compiler_version" != "default" ]; then
       sudo apt-get --allow-unauthenticated install -qq --force-yes gcc-${Compiler_version} g++-${Compiler_version}
     fi
   elif [ "$Compiler_name" = "clang" ]; then
-    export DEBIAN_FRONTEND=noninteractive
-
     # llvm-toolchain needed for more recent version of clang
-    echo "deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-6.0 main" | sudo tee -a /etc/apt/sources.list >/dev/null
+    wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
+    sudo -E apt-add-repository "deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-6.0 main"
     sudo -E apt-get -yq update &>> ~/apt-get-update.log
-    sudo -E apt-get -yq --allow-unauthenticated --no-install-suggests \
+    sudo -E apt-get -yq --no-install-suggests --allow-unauthenticated \
         --no-install-recommends $TRAVIS_APT_OPTS install clang-${Compiler_version}
   fi
 fi

.travis.yml

@@ -20,11 +20,15 @@ matrix:
       compiler: gcc
       env: Tr_Compiler_Version="8"
     - os: linux
+# clang
       compiler: clang
       env: Tr_Compiler_Version="default"
     - os: linux
       compiler: clang
       env: Tr_Compiler_Version="6.0"
+# osx
+    - os: osx
+      osx_image: xcode9.2
     - os: osx
       osx_image: xcode9.3beta