Pandoc from conda, with python 3.6

#208

.travis.yml

@@ -1,6 +1,7 @@
 language: python
 python:
   - "3.6"
+  - "3.6@conda"
   - "pypy"
   - "2.7"
   - "3.4"
@@ -12,20 +13,36 @@ matrix:
       sudo: required  # required for Python 3.7 (travis-ci/travis-ci#9069)
 
 install:
-  # command to install dependencies
-  - pip install -r requirements-dev.txt
-  - pip install -r requirements.txt
+  - if [[ "$TRAVIS_PYTHON_VERSION" == "3.6@conda" ]]; then
+      # We use conda in order to install pandoc
+      # https://docs.conda.io/projects/conda/en/latest/user-guide/tasks/use-conda-with-travis-ci.html
+      sudo apt-get update
+      wget https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O miniconda.sh;
+      bash miniconda.sh -b -p $HOME/miniconda
+      export PATH="$HOME/miniconda/bin:$PATH"
+      hash -r
+      conda config --set always_yes yes --set changeps1 no
+      conda update -q conda
+      conda config --append channels conda-forge
+      # Conda info
+      conda info -a
+      # Install dependencies
+      conda create -q -n jupytext-env python=$TRAVIS_PYTHON_VERSION --file requirements-dev.txt --file requirements.txt
+      source activate jupytext-env
+      conda install pandoc codecov -c conda-forge
+      pandoc -v
+    else
+      # command to install dependencies
+      pip install -r requirements-dev.txt
+      pip install -r requirements.txt
+    fi
   # install is required for testing the pre-commit mode
   - pip install .
   # install black if available (Python 3.6 and above), and autopep8 for testing the pipe mode
   - pip install black || true
   - pip install autopep8 || true
   # install sphinx_gallery and matplotlib if available (may not work on pypy)
   - pip install sphinx_gallery || true
-  # download and install pandoc 2.7.2
-  - wget https://github.com/jgm/pandoc/releases/download/2.7.2/pandoc-2.7.2-linux.tar.gz
-  - tar xvzf pandoc-2.7.2-linux.tar.gz
-  - PATH=pandoc-2.7.2/bin:$PATH pandoc -v
 before_script:
   # stop the build if there are Python syntax errors or undefined names
   - flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics