subprocess32 fails to install

[manuelli]

There seems to be a problem with one of matplotlib's dependencies which results in the following error during a docker build. I think this issue is related. I think this became an issue when scikit-image was added to the docker build.

Running setup.py install for subprocess32: started
    Running setup.py install for subprocess32: finished with status 'error'
    Complete output from command /usr/bin/python -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-yOFMXn/subprocess32/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /tmp/pip-xgyZdg-record/install-record.txt --single-version-externally-managed --compile:
    running install
    running build
    running build_py
    creating build
    creating build/lib.linux-x86_64-2.7
    copying subprocess32.py -> build/lib.linux-x86_64-2.7
    running build_ext
    building '_posixsubprocess' extension
    creating build/temp.linux-x86_64-2.7
    x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fno-strict-aliasing -Wdate-time -D_FORTIFY_SOURCE=2 -g -fstack-protector-strong -Wformat -Werror=format-security -fPIC -I/usr/include/python2.7 -c _posixsubprocess.c -o build/temp.linux-x86_64-2.7/_posixsubprocess.o
    _posixsubprocess.c:3:20: fatal error: Python.h: No such file or directory
    compilation terminated.
    error: command 'x86_64-linux-gnu-gcc' failed with exit status 1

[manuelli]

Seems to be working fine now.