add custom make command "make doctest_examples"

script:

  - if [[ "$DOCTEST_EXAMPLES" == "true" ]]; then

      cd docs && pip install -r requirements.txt;

      PYTHONWARNINGS= sphinx-build -M doctest ./ _build examples.rst;

      travis_terminate;

      make doctest_examples;

    fi

  - bash devtools/run_yapf.sh

  - bash devtools/run_flake8.sh

.PHONY: help Makefile

doctest_examples:

	export PYTHONWARNINGS= 

	@$(SPHINXBUILD) -M doctest "$(SOURCEDIR)" "$(BUILDDIR)" examples.rst;

# Catch-all target: route all unknown targets to Sphinx using the new

# "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).

%: Makefile