matminer dependency now broken due to pymatgen update

[ltalirz]

Steps to reproduce the problem

noticed in aiida-lsmo https://github.com/lsmo-epfl/aiida-lsmo/runs/2459918160

/opt/hostedtoolcache/Python/3.7.10/x64/lib/python3.7/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/test_oxidation_state.py:11: in <module>
    from aiida_lsmo.calcfunctions.oxidation_state import compute_oxidation_states
aiida_lsmo/calcfunctions/oxidation_state.py:5: in <module>
    import oximachinerunner
/opt/hostedtoolcache/Python/3.7.10/x64/lib/python3.7/site-packages/oximachinerunner/__init__.py:15: in <module>
    from oximachine_featurizer import featurize
/opt/hostedtoolcache/Python/3.7.10/x64/lib/python3.7/site-packages/oximachine_featurizer/__init__.py:9: in <module>
    from .featurize import FeatureCollector, GetFeatures, featurize
/opt/hostedtoolcache/Python/3.7.10/x64/lib/python3.7/site-packages/oximachine_featurizer/featurize.py:16: in <module>
    from matminer.featurizers.site import CrystalNNFingerprint, GaussianSymmFunc
/opt/hostedtoolcache/Python/3.7.10/x64/lib/python3.7/site-packages/matminer/featurizers/site.py:8: in <module>
    from matminer.utils.data import MagpieData
/opt/hostedtoolcache/Python/3.7.10/x64/lib/python3.7/site-packages/matminer/utils/data.py:17: in <module>
    from pymatgen import Element
E   ImportError: cannot import name 'Element' from 'pymatgen' (unknown location)

I guess you'll want to update the matminer dependency to a version that isn't broken (or restrict the pymatgen version <2021)

[kjappelbaum]

hm, i struggle sometimes to understand the dependency resolver ... because we fix a matminer version and they pin pymatgen. But I'll now also limit pymatgen here to a version without their new package system