KeyError could be suitable here

underworld2/underworld/swarm/_swarmvariable.py

Line 344 in b72fc39

except (UndefinedUnitError) as e:

Hi, I was recently trying to load a swarm variable without units and generated by an older version of underworld, the 'UndefinedUnitError' doesn't catch the exception which in my case threw a 'KeyError', changing this resulted in the loading to work as expected.
Sorry for not adding a file.

Hi @arijitlaik ,
Thanks for pointing this out! We have a fix for this that I applied to the _meshvariable and _swarm. I missed making this change here. I can apply now.

Thanks :)