Unable to follow through Add support to the KNoT command line interface

I have a clean install of Ubuntu 16 and I'm following the docs on KNoT Thing requirements.

When I tried to run `pip3 install --user -r $HOME/zephyr-knot-sdk/scripts/requirements.txt
` I got:
```
generating cffi module 'build/temp.linux-x86_64-3.5/_padding.c'
creating build/temp.linux-x86_64-3.5
generating cffi module 'build/temp.linux-x86_64-3.5/_constant_time.c'
generating cffi module 'build/temp.linux-x86_64-3.5/_openssl.c'
building '_openssl' extension
creating build/temp.linux-x86_64-3.5/build
creating build/temp.linux-x86_64-3.5/build/temp.linux-x86_64-3.5
x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -I/usr/include/python3.5m -c build/temp.linux-x86_64-3.5/_openssl.c -o build/temp.linux-x86_64-3.5/build/temp.linux-x86_64-3.5/_openssl.o -Wconversion -Wno-error=sign-conversion
build/temp.linux-x86_64-3.5/_openssl.c:22:24: fatal error: pyconfig.h: No such file or directory
compilation terminated.
error: command 'x86_64-linux-gnu-gcc' failed with exit status 1

----------------------------------------
Command "/usr/bin/python3 -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-z9ev1zjz/cryptography/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-en0_nxlj-record/install-record.txt --single-version-externally-managed --compile --user --prefix=" failed with error code 1 in /tmp/pip-build-z9ev1zjz/cryptography/
```

Quick google led me to a solution installing python3-dev `sudo apt-get install python3-dev`

Then running the command again
```

Building wheels for collected packages: cryptography
Running setup.py bdist_wheel for cryptography ... done
Stored in directory: /home/pauloserrafh/.cache/pip/wheels/13/ad/1b/94b787de6776646c28a03dc2f4a6387e3ab375533028c58195
Successfully built cryptography
Installing collected packages: asn1crypto, pycparser, cffi, Click, colorama, humanfriendly, coloredlogs, idna, six, cryptography, docopt, intelhex, prettytable, pyelftools, python-dateutil, PyYAML, pykwalify, pyserial
Successfully installed Click-7.0 PyYAML-4.2b1 asn1crypto-0.24.0 cffi-1.11.5 colorama-0.4.1 coloredlogs-10.0 cryptography-2.4.2 docopt-0.6.2 humanfriendly-4.18 idna-2.8 intelhex-2.2.1 prettytable-0.7.2 pycparser-2.19 pyelftools-0.25 pykwalify-1.7.0 pyserial-3.4 python-dateutil-2.8.0 six-1.12.0
```

Perhaps the apt install for python3-dev should be added or something else is missing. Need to re-check to make sure the problem is reproducible and its not an issue with my setup only (even if it is some thing more specific, might be worth add a note)