PL shouldn't override PYTHONWARNINGS
🐛 Bug
This is bad:

  
    
      pytorch-lightning/pytorch_lightning/trainer/trainer.py
    
    
         Line 71
      in
      c208ac6
    
  
  
    

        
          
           os.environ['PYTHONWARNINGS'] = 'ignore:semaphore_tracker:UserWarning' 
        
    
  


What a user to do if they need to use PYTHONWARNINGS?
Adding to the existing setting is the way, but overriding it is taking away control from the user.
And after removing this override I still can't figure why I'm getting these:
PYTHONWARNINGS=ignore python -c "import pytorch_lightning"
/home/stas/anaconda3/envs/main-38/lib/python3.8/site-packages/wandb/util.py:36: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and in 3.9 it will stop working
  from collections import namedtuple, Mapping, Sequence
/home/stas/anaconda3/envs/main-38/lib/python3.8/site-packages/wandb/vendor/graphql-core-1.1/graphql/type/directives.py:55: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and in 3.9 it will stop working
  assert isinstance(locations, collections.Iterable), 'Must provide locations for directive.'

PYTHONWARNINGS=ignore / -W ignore doesn't get rid of those.
There must be yet another override somewhere else.
I reported the deprecations wandb/client#1503, but clearly something in PL or its dependencies is stealing user's control away still.
Thanks.