Workaround cython/cython#4172

Author: rainwoodman

setup.py

@@ -375,7 +375,12 @@ def run(self):
 # Note: if not using `cythonize`, coverage can be enabled by
 # pinning `ext.cython_directives = directives` to each ext in extensions.
 # github.com/cython/cython/wiki/enhancements-compilerdirectives#in-setuppy
-directives = {"linetrace": False, "language_level": 3}
+directives = {"linetrace": False,
+              "language_level": 3,
+              # Use cython 0.29.x binop methods.
+              # See https://github.com/cython/cython/issues/4172
+              "c_api_binop_methods": True,
+              }
 macros = []
 if linetrace:
     # https://pypkg.com/pypi/pytest-cython/f/tests/example-project/setup.py