Issue with rdflib-shim

[vemonet]

Hi @hsolbrig !

I have tried to use install PyShEx in a project using RDFLib 6 and I got this error:

File "/app/./app/api/validation.py", line 14, in <module>
    from pyshex import ShExEvaluator
  File "/usr/local/lib/python3.8/site-packages/pyshex/__init__.py", line 1, in <module>
    from pyshex.prefixlib import PrefixLibrary, standard_prefixes, known_prefixes
  File "/usr/local/lib/python3.8/site-packages/pyshex/prefixlib.py", line 4, in <module>
    from pyshexc.parser_impl.generate_shexj import load_shex_file
  File "/usr/local/lib/python3.8/site-packages/pyshexc/__init__.py", line 2, in <module>
    shimin = rdflib_shim.RDFLIB_SHIM
AttributeError: module 'rdflib_shim' has no attribute 'RDFLIB_SHIM'

Any idea what it could be due to?