Update OSX image

.travis.yml

@@ -2,7 +2,7 @@ matrix:
   include:
     - name: "MacOS + Clang"
       os: osx
-      osx_image: xcode10.1
+      osx_image: xcode10.2
       compiler: clang
       before_install:
         - pip3 install -r requirements.txt
@@ -23,7 +23,7 @@ matrix:
             - astyle
     - name: "MacOS + GCC8"
       os: osx
-      osx_image: xcode10.1
+      osx_image: xcode10.2
       compiler: gcc
       addons:
         homebrew: