running python3 setup.py resulted in the following error message that was fixed by adding NULL after return in lines 265 and 269:
running python3 setup.py resulted in the following error message that was fixed by adding NULL after return in lines 265 and 269:

src/esm.c:265:9: error: non-void function 'PyInit_esm' should return a value
      [-Wreturn-type]
        return;
        ^
src/esm.c:269:9: error: non-void function 'PyInit_esm' should return a value
      [-Wreturn-type]
        return;
        ^
2 errors generated.
error: command 'gcc' failed with exit status 1
mangelin/esmre,mangelin/esmre