Here is an example to use to test for this bug.
Proper use on my computer (PYTHONPATH may need adjusting on other systems):
Python2:
cd small_example
python setup.py build_ext build install --prefix=`pwd`
export PYTHONPATH=`pwd`/lib64/python2.7/site-packages
cd test
python a_test.py
# outputs 3
Python3:
cd small_example
python3 setup.py build_ext build install --prefix=`pwd`
export PYTHONPATH=`pwd`/lib64/python3.4/site-packages
cd test
python3 a_test.py
# outputs 3
Clean files:
rm -Rf build/ lib/ lib64/ example/example.py example/example_wrap.cpp *~ example/__pycache__/
Check for the bug:
export CXX="env BAR=FOO g++"
or
export CXX="ccache g++"
etc
Then run either the Python2 or Python3 test, and it will fail if this bug has not been fixed.