Exclude python venv directory

I have a folder that contains python scripts, which also includes virtual environment files - a folder which often contains tens of thousands of files, and I just don't want those directories sync'd. 

Prior to the recent sync changes, I would exclude that folder from syncing, and then recreate it and it would be ignored. So my workflow would be 

mkdir env
dropbox exclude add env 
mkdir env 

at which point I could add anything to env and it wouldn't be sync'd 

using that workflow now creates a folder called `env (Selective Sync Conflict)` which is sync'd. 

Any thoughts how I can achieve this now?