Failing and long running examples

[maxnus]

The following examples are currently failing on the GHA server:

2023-09-22T20:27:28.9603626Z FAILED vayesta/tests/test_examples.py::test_example[variational_embedding/01-simple-vembedding.py] - ModuleNotFoundError: pygnme is required for variational embedding approaches.
2023-09-22T20:27:28.9605053Z FAILED vayesta/tests/test_examples.py::test_example[edmet/01-1d-hubbard-comparison.py] - ModuleNotFoundError: No module named 'matplotlib'
2023-09-22T20:27:28.9605621Z FAILED vayesta/tests/test_examples.py::test_example[edmet/72-h-chain-benchmark.py] - TypeError: unsupported operand type(s) for -: 'NoneType' and 'float'
2023-09-22T20:27:28.9607444Z FAILED vayesta/tests/test_examples.py::test_example[other/71-sc-h-ring.py] - RuntimeError: MF not symmetric under Rotation(0,0,1.0472)
2023-09-22T20:27:28.9608001Z FAILED vayesta/tests/test_examples.py::test_example[molecules/40-spectral-moments.py] - AttributeError: module 'pyscf.cc' has no attribute 'gfccsd'
2023-09-22T20:27:28.9608620Z FAILED vayesta/tests/test_examples.py::test_example[molecules/20-dump-clusters.py] - ValueError: Error; solver Dump not available for restricted purely electronic systems

The first two are missing dependencies. Should pygnme be requested for CI, also in light of #125?

Furthermore, the following examples timed out after 5 min:

2023-09-22T20:27:28.9609088Z FAILED vayesta/tests/test_examples.py::test_example[molecules/25-externally-correct.py] - Failed: Timeout >300.0s
2023-09-22T20:27:28.9606065Z FAILED vayesta/tests/test_examples.py::test_example[solids/20-mRPA-interactions.py] - Failed: Timeout >300.0s
2023-09-22T20:27:28.9606492Z FAILED vayesta/tests/test_examples.py::test_example[solids/61-start-from-lda.py] - Failed: Timeout >300.0s
2023-09-22T20:27:28.9606931Z FAILED vayesta/tests/test_examples.py::test_example[solids/04-kpts-vs-supercell.py] - Failed: Timeout >300.0s
2023-09-22T20:27:28.9604070Z FAILED vayesta/tests/test_examples.py::test_example[dmet/70-h-ring-benchmark.py] - Failed: Timeout >300.0s
2023-09-22T20:27:28.9604518Z FAILED vayesta/tests/test_examples.py::test_example[edmet/70-h-ring-benchmark-df.py] - Failed: Timeout >300.0s
2023-09-22T20:27:28.9602958Z FAILED vayesta/tests/test_examples.py::test_example[examples/run_examples.py] - Failed: Timeout >300.0s

Perhaps the example owners could have a try to bring the runtime down, by reducing the system size, basis size, or number of self-consistency cycles via increasing the tolerance.