Installing libffi-dev and re-installing python3.7 fixed the problem for me.

to cleanly build py 3.7 libffi-dev is required or else later stuff will fail

If using RHEL/Fedora:

yum install libffi-devel

or

sudo dnf install libffi-devel

If using Debian/Ubuntu:

sudo apt-get install libffi-dev

On a fresh Debian image, cloning https://github.com/python/cpython and running:

sudo apt-get updatesudo apt-get upgradesudo apt-get dist-upgradesudo apt-get install build-essential python-dev python-setuptools python-pip python-smbussudo apt-get install libncursesw5-dev libgdbm-dev libc6-devsudo apt-get install zlib1g-dev libsqlite3-dev tk-devsudo apt-get install libssl-dev opensslsudo apt-get install libffi-dev

Now execute the configure file cloned above:

./configuremake # alternatively `make -j 4` will utilize 4 threadssudo make altinstall

Got 3.7 installed and working for me.

SLIGHT UPDATE

Looks like I said I would update this answer with some more explanation and two years later I don't have much to add.

• this SO post explains why certain libraries like python-dev might be necessary.
• this SO post explains why one might use the altinstall as opposed to install argument in the make command.

Aside from that I guess the choice would be to either read through the cpython codebase looking for #include directives that need to be met, but what I usually do is keep trying to install the package and just keep reading through the output installing the required packages until it succeeds.

Reminds me of the story of the Engineer, the Manager and the Programmer whose car rolls down a hill.

If you use pyenv and get error "No module named '_ctypes'" (like i am) on Debian/Raspbian/Ubuntu you need to run this commands:

sudo apt-get install libffi-devpyenv uninstall 3.7.6pyenv install 3.7.6

Put your version of python instead of 3.7.6