investigate arm64 platform differences

[mikemhenry]

running the tests on arm64 linux box, I got some failures:

FAILED tests/protocols/openmm_septop/test_septop_protocol.py::test_validate_complex_endstates_protcomp[stateA-benzene_system-benzene_complex_system] - TypeError: Object of type Mol is not JSON serializable
FAILED tests/protocols/openmm_septop/test_septop_protocol.py::test_validate_complex_endstates_protcomp[stateB-benzene_complex_system-benzene_system] - TypeError: Object of type Mol is not JSON serializable
FAILED tests/protocols/openmm_septop/test_septop_protocol.py::test_validate_complex_endstates_nosolvcomp[stateA-T4L_benzene_vacuum-benzene_complex_system] - TypeError: Object of type Mol is not JSON serializable
FAILED tests/protocols/openmm_septop/test_septop_protocol.py::test_validate_complex_endstates_nosolvcomp[stateB-benzene_complex_system-T4L_benzene_vacuum] - TypeError: Object of type Mol is not JSON serializable
FAILED tests/protocols/openmm_septop/test_septop_protocol.py::test_validate_alchem_comps_missing[stateA-T4L_system-benzene_complex_system] - TypeError: Object of type Mol is not JSON serializable
FAILED tests/protocols/openmm_septop/test_septop_protocol.py::test_validate_alchem_comps_missing[stateB-benzene_complex_system-T4L_system] - TypeError: Object of type Mol is not JSON serializable
FAILED tests/test_ligand_network.py::TestLigandNetwork::test_to_graphml - assert '<graphml xml...>\n</graphml>' == '<graphml xml...>\n</graphml>'
FAILED tests/test_ligand_network.py::TestLigandNetwork::test_from_graphml - assert <LigandNetwork-65a3804adfd4a3c15fdde27d03df5e7d> == <LigandNetwork-d440e118bbd483802321dd3a46059cd1>

I will investigate this further.