% pyenv install 3.8.3
python-build: use openssl@1.1 from homebrew
python-build: use readline from homebrew
Downloading Python-3.8.3.tar.xz...
-> https://www.python.org/ftp/python/3.8.3/Python-3.8.3.tar.xz
Installing Python-3.8.3...
python-build: use readline from homebrew
python-build: use zlib from xcode sdk

BUILD FAILED (OS X 10.16 using python-build 20180424)

Inspect or clean up the working tree at /var/folders/sl/5j1zvmtj0gb8qpgkklkf38dh0000gr/T/python-build.20200626170507.14625
Results logged to /var/folders/sl/5j1zvmtj0gb8qpgkklkf38dh0000gr/T/python-build.20200626170507.14625.log

Last 10 log lines:
./Modules/posixmodule.c:9141:12: note: forward declaration of 'struct sf_hdtr'
    struct sf_hdtr sf;
           ^
./Modules/posixmodule.c:9221:15: error: implicit declaration of function 'sendfile' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        ret = sendfile(in, out, offset, &sbytes, &sf, flags);
              ^
2 errors generated.
make: *** [Modules/posixmodule.o] Error 1
make: *** Waiting for unfinished jobs....
1 warning generated.