check integer correctly to account for pyscf #2377

[MatthewRHermes]

isinstance (*, int) -> isinstance (*, (int, np.integer))

[fishjojo]

There is a function isinteger in lib.misc that we can use.

[MatthewRHermes]

I wanted to update the github-actions to validate that I didn't miss anything but I really can't at this point due to #67

[MatthewRHermes]

Changed the title because on closer inspection I don't think this is a numpy 2.0 thing. Not sure what it is but it was a problem on my machines (python 3.9.19, numpy 1.24.3 and python 3.8.5, numpy 1.23.5).

[MatthewRHermes]

OK, figured out why this became a problem for me now: pyscf #2377 changed the data type of libxc.XC_CODES.values () from native Python integer to numpy.intc in order to interface with libxc functional keyword parsing. The reason the github actions isn't catching this is, as in #67, we need the PySCF 2.7 release in order to see the effects of pyscf #2377.