Variables with no "units" attribute cause a crash by AttributeError (cfunits 3.3.7)

[FObersteiner]

cf-checker/src/cfchecker/cfchecks.py

Line 3037 in c0486c6

except TypeError:

this line just caused on my system:

Traceback (most recent call last):
  File "/home/user/Code/Python/nc-checkers/cf-checker/.venv/bin/cfchecks", line 10, in <module>
    sys.exit(main())
             ~~~~^^
  File "/home/user/Code/Python/nc-checkers/cf-checker/.venv/lib/python3.13/site-packages/cfchecker/cfchecks.py", line 3402, in main
    inst.checker(file)
    ~~~~~~~~~~~~^^^^^^
  File "/home/user/Code/Python/nc-checkers/cf-checker/.venv/lib/python3.13/site-packages/cfchecker/cfchecks.py", line 531, in checker
    return self._checker()
           ~~~~~~~~~~~~~^^
  File "/home/user/Code/Python/nc-checkers/cf-checker/.venv/lib/python3.13/site-packages/cfchecker/cfchecks.py", line 823, in _checker
    self.chkTimeVariableAttributes(var)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/home/user/Code/Python/nc-checkers/cf-checker/.venv/lib/python3.13/site-packages/cfchecker/cfchecks.py", line 2931, in chkTimeVariableAttributes
    varUnits = Units(var.units)
                     ^^^^^^^^^
  File "src/netCDF4/_netCDF4.pyx", line 5030, in netCDF4._netCDF4.Variable.__getattr__
  File "src/netCDF4/_netCDF4.pyx", line 4752, in netCDF4._netCDF4.Variable.getncattr
  File "src/netCDF4/_netCDF4.pyx", line 1667, in netCDF4._netCDF4._get_att
  File "src/netCDF4/_netCDF4.pyx", line 2164, in netCDF4._netCDF4._ensure_nc_success
AttributeError: NetCDF: Attribute not found

...which basically means that the Units class returns an AttributeError, not a TypeError. This might be a version thing (I'm using cfunits 3.3.7 as the requirements.txt does not specify a specific version). I worked around by using except (AttributeError, TypeError): instead of just the TypeError in the line quoted at the start of this post.

Edit: here's a file to reproduce the issue: https://thredds.atmohub.kit.edu/thredds/fileServer/iagos-caribic/IAGOS-CARIBIC_WSM_files_collection_20240717/CARIBIC-1/WSM_19980109_012_CMB_MUC_V01.nc