'lpsolve.pxd' not found in clara/pylpsolve.pyx

[LioTree]

I encountered this problem while running make on Ubuntu 20.04 with Python 3.8.10:

Error compiling Cython file:
------------------------------------------------------------
...
from array import array
from cpython cimport array as c_array
from libc.stdio cimport stdout, stderr


cimport lpsolve
        ^
------------------------------------------------------------

clara/pylpsolve.pyx:10:8: 'lpsolve.pxd' not found

This is because the default search path for cimport does not include ./clara/. It needs to be manually added to the search path.

Line 18 of setup.py needs to be changed to:

ext_modules = cythonize(extensions, include_path=["./clara"]),