xcfunctional tests failing following PySCF v2.7.0 release

[hatemhelal]

          Might be a coincidence but our unittests started failing today and I noticed there is a new PySCF release as of the past few hours.  Will investigate further...

Originally posted by @hatemhelal in #11 (comment)

Here is a snippet from the pytest run:

=========================== short test summary info ============================
FAILED test/test_xcfunctional.py::test_lda[lda_exchange] - AssertionError: 
Not equal to tolerance rtol=1e-07, atol=1e-07

Mismatched elements: 302 / 7936 (3.81%)
Max absolute difference among violations: 9.28646817e-06
Max relative difference among violations: inf
 ACTUAL: array([0., 0., 0., ..., 0., 0., 0.])
 DESIRED: array([0., 0., 0., ..., 0., 0., 0.])
FAILED test/test_xcfunctional.py::test_gga[gga_exchange_b88] - AssertionError: 
Not equal to tolerance rtol=1e-07, atol=1e-06

Mismatched elements: 302 / 7936 (3.81%)
Max absolute difference among violations: 0.20184576
Max relative difference among violations: inf
 ACTUAL: array([0., 0., 0., ..., 0., 0., 0.])
 DESIRED: array([0., 0., 0., ..., 0., 0., 0.])
FAILED test/test_xcfunctional.py::test_gga[gga_exchange_pbe] - AssertionError: 
Not equal to tolerance rtol=1e-07, atol=1e-06

Mismatched elements: 302 / 7936 (3.81%)
Max absolute difference among violations: 1.67527886e-05
Max relative difference among violations: inf
 ACTUAL: array([-0., -0., -0., ..., -0., -0., -0.])
 DESIRED: array([0., 0., 0., ..., 0., 0., 0.])
FAILED test/test_xcfunctional.py::test_gga[gga_correlation_lyp] - AssertionError: 
Not equal to tolerance rtol=1e-07, atol=1e-06

Mismatched elements: 302 / 7936 (3.81%)
Max absolute difference among violations: 1.77179295e-06
Max relative difference among violations: inf
 ACTUAL: array([0., 0., 0., ..., 0., 0., 0.])
 DESIRED: array([0., 0., 0., ..., 0., 0., 0.])
======== 4 failed, 42 passed, 3 skipped, 1 xfailed in 140.31s (0:02:20) ========

[hatemhelal]

By downgrading to pyscf==2.6.2 I have these tests passing locally but upgrading to pyscf==2.7.0 I can reproduce the failures flagged by the CI.

To temporarily get the CI green I will pin the pyscf version and keep this issue open for further investigation.