Nexus: Pass PYTHONPATH recorded at cmake step to nxs-test.

[ye-luo]

Proposed changes

I can reproduce nxs-test issue of sulfur on my workstation.
Both python interpreter and PYTHONPATH must be properly propagated to all the cmake to python and python internal calls.
Previous issues

1. nxs-test --pythonpath wipes out necessary PYTHONPATH
2. All nexus internal calls to python scripts doesn't enforce parent python interpreter. There might be more fixes needed. I only found those covered by ctest.

With this PR, at the CMake step, recorded python environment will be used for ctest. Even the environment is changed after cmake, ctest runs in the recorded environment. Updating test environment requires rerun cmake.

What type(s) of changes does this code introduce?

• Bugfix

Does this introduce a breaking change?

• No

What systems has this change been tested on?

epyc-server

Checklist

• Yes. This PR is up to date with current the current state of 'develop'

[prckent]

Quick gcc build on sulfur shows that this fixes the persistent problems. i.e. Cures about 12 x number of builds failures on cdash. Thanks Ye. Note that I only ran the PR and I did not search for any "missed" updates in nexus/our cmake.

Output of ctest -L deterministic below.

Before:

99% tests passed, 12 tests failed out of 1139

Label Time Summary:
QMCPACK                     = 269.25 sec*proc (62 tests)
QMCPACK-checking-results    =  52.83 sec*proc (893 tests)
converter                   =  14.54 sec*proc (20 tests)
deterministic               = 532.33 sec*proc (1139 tests)
nexus                       =  60.45 sec*proc (70 tests)
quality_unknown             = 507.86 sec*proc (1104 tests)
unit                        =  36.48 sec*proc (45 tests)

Total Test time (real) =  38.93 sec

The following tests FAILED:
        2206 - ntest_nexus_nxs_sim (Failed)
        2207 - ntest_nexus_qmca (Failed)
        2208 - ntest_nexus_qmc_fit (Failed)
        2209 - ntest_nexus_qdens (Failed)
        2211 - ntest_nexus_example_gamess_H2O (Failed)
        2212 - ntest_nexus_example_pwscf_relax_Ge_T (Failed)
        2213 - ntest_nexus_example_qmcpack_H2O (Failed)
        2214 - ntest_nexus_example_qmcpack_LiH (Failed)
        2215 - ntest_nexus_example_qmcpack_c20 (Failed)
        2216 - ntest_nexus_example_qmcpack_diamond (Failed)
        2217 - ntest_nexus_example_qmcpack_graphene (Failed)
        2218 - ntest_nexus_example_qmcpack_oxygen_dimer (Failed)
Errors while running CTest

After:

100% tests passed, 0 tests failed out of 1139

Label Time Summary:
QMCPACK                     = 271.16 sec*proc (62 tests)
QMCPACK-checking-results    =  53.31 sec*proc (893 tests)
converter                   =  14.81 sec*proc (20 tests)
deterministic               = 556.09 sec*proc (1139 tests)
nexus                       =  79.94 sec*proc (70 tests)
quality_unknown             = 531.27 sec*proc (1104 tests)
unit                        =  37.02 sec*proc (45 tests)

Total Test time (real) =  43.39 sec

[ye-luo]

Test this please