This is similar to: https://bugs.python.org/issue28190

Not cross-compiling, but using a different ncurses version than is provided under /usr/include/ncursesw

Specifying CPPFLAGS to have "-I/path/to/ncurses/include" does not override the "/usr/include/ncursesw" in setup.py

        if curses_library == 'ncursesw':
            curses_defines.append(('HAVE_NCURSESW', '1'))
            if not cross_compiling:
                curses_includes.append('/usr/include/ncursesw')

Python 2.7.x does not have this issue, but 3.6.x and 3.7.x do.  2 and 3 have different ways of setting up the include path for curses when building the extension.

In my case, removing the curses_include.append from setup.py results in a working extension.

It probably makes sense that Extension(include_dirs=) take priority over Python build CPPFLAGS, setup.py may need to be more cautious about adding the ncurses include path.

Only tested in 2.7, 3.6, 3.7.

This explains some of the build/linkage problems encountered in issue #36630, and that I encountered while working on issue #36982.