After updating conda I get a CommandNotFoundError for conda

This cropped up for me today too. It appears to be a bug in conda 4.6.9.
I deleted everything conda-related but C:\Users\[username]\Anaconda3 and C:\Users\[username]\Anaconda3\Scripts from my PATH and conda commands started working. I still couldn't run source activate [environment] in bash without getting:

CommandNotFoundError: No command 'conda conda'

So I downgraded to 4.6.8 with:

conda install conda=4.6.8

And it solved my problem.