travis CHANGE update gcc for libyang
diff --git a/.travis.yml b/.travis.yml
index 3375cd7..35a362f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,6 +10,14 @@
       dist: trusty
       sudo: required
       compiler: gcc
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+          packages:
+            - g++-7
+      env:
+        - MATRIX_EVAL="CC=gcc-7 && CXX=g++-7"
     - os: osx
       compiler: gcc
   allow_failures:
@@ -21,6 +29,7 @@
     - devel
 
 before_install:
+  - eval "${MATRIX_EVAL}"
   - if [ "$TRAVIS_OS_NAME" = "linux" ]; then bash .travis-deps-linux.sh; fi
   - if [ "$TRAVIS_OS_NAME" = "linux" -a "$CC" = "gcc" ]; then pip install --user codecov; export CFLAGS="-coverage"; fi
   - if [ "$TRAVIS_OS_NAME" = "osx" ]; then bash .travis-deps-osx.sh; fi