title: Building pynauty with python3
body: <p>I am trying to build pynauty according to this instructions:
  <a href="https://web.cs.dal.ca/~peter/software/pynauty/html/install.html#build" rel="nofollow noreferrer">https://web.cs.dal.ca/~peter/software/pynauty/html/install.html#build</a></p>
  
  <p>I would like point out that my main goal is to run this python code:
  <a href="https://github.com/calebh/dihash" rel="nofollow noreferrer">https://github.com/calebh/dihash</a></p>
  
  <p>Sadly I can not pass the pynauty's make phase.
  If I execute <code>make pynauty</code> command I get the following error:</p>
  
  <pre><code>cd nauty; make nauty.o nautil.o naugraph.o schreier.o naurng.o
  make[1]: Entering directory '/home/pc/pynauty-0.6.0/nauty27rc5'
  make[1]: 'nauty.o' is up to date.
  make[1]: 'nautil.o' is up to date.
  make[1]: 'naugraph.o' is up to date.
  make[1]: 'schreier.o' is up to date.
  make[1]: 'naurng.o' is up to date.
  make[1]: Leaving directory '/home/pc/pynauty-0.6.0/nauty27rc5'
  python setup.py build
  running build
  running build_py
  running build_ext
  building 'pynauty.nautywrap' extension
  x86_64-linux-gnu-gcc -pthread -fno-strict-aliasing -Wdate-time -D_FORTIFY_SOURCE=2 -g -fdebug-prefix-map=/build/python2.7-8kFkPd/python2.7-2.7.17=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC -Inauty -Isrc -I/usr/include/python2.7 -c src/nautywrap.c -o build/temp.linux-x86_64-2.7/src/nautywrap.o -O4 -fPIC
  src/nautywrap.c:15:10: fatal error: Python.h: No such file or directory
     15 | #include &lt;Python.h&gt;
        |          ^~~~~~~~~~
  compilation terminated.
  error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
  make: *** [Makefile:36: pynauty] Error 1
  </code></pre>
  
  <p>I guess the above is because I don't have <code>python-dev</code>  package installed (I want to build if for python3). So I've added an alias for python3 with:
  <code>aliast python=python3</code>.
  But still when I type <code>make</code> in the pynauty's root directory I get a message saying that python2 is detected:</p>
  
  <pre><code>Available targets:
  
    pynauty       - build the pynauty extension module
    tests         - run all tests
    clean         - remove all python related temp files and dirs
    user-ins      - install pynauty into ~/.local/
    user-unins    - uninstall pynauty from ~/.local/
    virtenv-ins   - install pynauty into the active virtualenv
    virtenv-unins - uninstall pynauty from the active virtualenv
    dist          - create a source distribution
    docs          - build pyanauty documentation
    clean-docs    - remove pyanauty documentation
    nauty-objects - compile only nauty.o nautil.o naugraph.o schreier.o naurng.o
    nauty-progs   - build all nauty programs
    clean-nauty   - a "distclean" for nauty
    clobber       - clean + clean-nauty + clean-docs
  
  Python version: 2 7 17
  Machine type: x86_64
  </code></pre>