ORM: Remove pymatgen version check in StructureData.set_pymatgen_structure

[unkcpz]

Don't know what happened exactly, but if I don't do this, I'll get the exception:

...
 File "/home/jovyan/aiida-core/aiida/orm/nodes/data/cif.py", line 764, in get_structure
    result = convert_function(cif=self, parameters=parameters, metadata={'store_provenance': store})
  File "/home/jovyan/aiida-core/aiida/engine/processes/functions.py", line 179, in decorated_function
    result, _ = run_get_node(*args, **kwargs)
  File "/home/jovyan/aiida-core/aiida/engine/processes/functions.py", line 152, in run_get_node
    result = process.execute()
  File "/home/jovyan/aiida-core/aiida/engine/processes/functions.py", line 366, in execute
    result = super().execute()
  File "/opt/conda/lib/python3.9/site-packages/plumpy/processes.py", line 86, in func_wrapper
    return func(self, *args, **kwargs)
  File "/opt/conda/lib/python3.9/site-packages/plumpy/processes.py", line 1172, in execute
    return self.future().result()
  File "/opt/conda/lib/python3.9/site-packages/plumpy/process_states.py", line 228, in execute
    result = self.run_fn(*self.args, **self.kwargs)
  File "/home/jovyan/aiida-core/aiida/engine/processes/functions.py", line 410, in run
    result = self._func(*args, **kwargs)
  File "/home/jovyan/aiida-core/aiida/tools/data/cif.py", line 152, in _get_aiida_structure_pymatgen_inline
    return {'structure': StructureData(pymatgen_structure=structures[0])}
  File "/home/jovyan/aiida-core/aiida/orm/nodes/data/structure.py", line 742, in __init__
    self.set_pymatgen_structure(pymatgen_structure)
  File "/home/jovyan/aiida-core/aiida/orm/nodes/data/structure.py", line 827, in set_pymatgen_structure
    from pkg_resources import parse_version
  File "/opt/conda/lib/python3.9/site-packages/pkg_resources/__init__.py", line 3268, in <module>
    def _initialize_master_working_set():
  File "/opt/conda/lib/python3.9/site-packages/pkg_resources/__init__.py", line 3251, in _call_aside
    f(*args, **kwargs)
  File "/opt/conda/lib/python3.9/site-packages/pkg_resources/__init__.py", line 3293, in _initialize_master_working_set
    tuple(
  File "/opt/conda/lib/python3.9/site-packages/pkg_resources/__init__.py", line 3294, in <genexpr>
    dist.activate(replace=False)
  File "/opt/conda/lib/python3.9/site-packages/pkg_resources/__init__.py", line 2805, in activate
    declare_namespace(pkg)
  File "/opt/conda/lib/python3.9/site-packages/pkg_resources/__init__.py", line 2304, in declare_namespace
    _handle_ns(packageName, path_item)
  File "/opt/conda/lib/python3.9/site-packages/pkg_resources/__init__.py", line 2221, in _handle_ns
    loader = importer.find_module(packageName)
  File "<frozen importlib._bootstrap_external>", line 493, in _find_module_shim
  File "<frozen importlib._bootstrap_external>", line 1428, in find_loader
  File "<frozen importlib._bootstrap_external>", line 1473, in find_spec
  File "<frozen importlib._bootstrap_external>", line 64, in _path_join
  File "<frozen importlib._bootstrap_external>", line 64, in <listcomp>
AttributeError: 'PosixPath' object has no attribute 'rstrip'

[sphuber]

I think we can just remove the version check, since we require pymatgen>=2019.7.2 in the pyproject.toml. So just always use the case with the new feature, and then you can get rid of the version check entirely.

[unkcpz]

@sphuber thanks! I'll update this PR for it.

[sphuber]

Thanks @unkcpz