Use unsupported xenial build environment on Travis

.travis.yml

@@ -1,20 +1,18 @@
 sudo: required
-dist: trusty
+dist: xenial
 language: python
 python:
-  - "3.4"
   - "3.5"
   - "3.6"
+  - "3.7"
 addons:
   apt:
-    sources:
-      - ubuntu-toolchain-r-test
     packages:
-      - gcc-4.9
-      - g++-4.9
-      - gfortran-4.9
+      - gfortran
       - mpich
       - libmpich-dev
+      - libhdf5-serial-dev
+      - libhdf5-mpich-dev
 cache:
   directories:
   - $HOME/nndc_hdf5
@@ -30,18 +28,11 @@ env:
     - OPENMC_MULTIPOLE_LIBRARY=$HOME/multipole_lib
     - PATH=$PATH:$HOME/NJOY2016/build
     - DISPLAY=:99.0
-    - CC=gcc-4.9
-    - CXX=g++-4.9
-    - FC=gfortran-4.9
   matrix:
     - OMP=n MPI=n PHDF5=n
     - OMP=y MPI=n PHDF5=n
     - OMP=n MPI=y PHDF5=n
     - OMP=n MPI=y PHDF5=y
-before_install:
-  - sudo add-apt-repository ppa:nschloe/hdf5-backports -y
-  - sudo apt-get update -q
-  - sudo apt-get install libhdf5-serial-dev libhdf5-mpich-dev -y
 install:
   - ./tools/ci/travis-install.sh
 before_script:

tools/ci/travis-install-njoy.sh

@@ -3,6 +3,5 @@ set -ex
 cd $HOME
 git clone https://github.com/njoy/NJOY2016
 cd NJOY2016
-sed -i -e 's/5\.1/4.8/' CMakeLists.txt
 mkdir build && cd build
 cmake -Dstatic=on .. && make 2>/dev/null && sudo make install

tools/ci/travis-install.sh

@@ -16,11 +16,6 @@ pip install cython
 # pytest installed by default -- make sure we get latest
 pip install --upgrade pytest
 
-# Pandas stopped supporting Python 3.4 with version 0.21
-if [[ $TRAVIS_PYTHON_VERSION == "3.4" ]]; then
-    pip install pandas==0.20.3
-fi
-
 # Install mpi4py for MPI configurations
 if [[ $MPI == 'y' ]]; then
     pip install --no-binary=mpi4py mpi4py

tools/ci/travis-script.sh

@@ -2,7 +2,7 @@
 set -ex
 
 # Run source check
-if [[ $TRAVIS_PYTHON_VERSION == "3.4" && $OMP == 'n' && $MPI == 'n' ]]; then
+if [[ $TRAVIS_PYTHON_VERSION == "3.5" && $OMP == 'n' && $MPI == 'n' ]]; then
     pushd tests && python check_source.py && popd
 fi