using gcc 5

.travis.yml

@@ -4,7 +4,7 @@ python:
   - "3.6"
 # command to install dependencies
 sudo: enabled
-dist: xenial
+dist: trusty
 addons:
   apt:
     packages:
@@ -15,6 +15,13 @@ addons:
 install:
   # We do this conditionally because it saves us some downloading if the
   # version is the same.
+  - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+  - sudo apt-get -qq update
+  - sudo apt-get -qq install g++-5
+  - sudo apt-get -qq install gcc-5
+  - sudo apt-get -qq install gfortran-5
+  # - export CXX="g++-6" CC="gcc-6"
+  - sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-5 60 --slave /usr/bin/g++ g++ /usr/bin/g++-5 --slave /usr/bin/gfortran gfortran /usr/bin/gfortran-5
   - wget https://repo.continuum.io/miniconda/Miniconda3-4.3.21-Linux-x86_64.sh -O miniconda.sh
   - bash miniconda.sh -b -p $HOME/miniconda
   - export PATH="$HOME/miniconda/bin:$PATH"