stexls and python 3.9

[kohlhase]

I am on python 3.9 and (finally) wanted to use the trefier. But I get

upgrade-w-trefier 
Processing /Users/kohlhase/vc/git/github.com/sLaTeX/stexls
Requirement already satisfied: antlr4-python3-runtime>=4.8 in /usr/local/lib/python3.9/site-packages (from stexls==4.4.2) (4.8)
Requirement already satisfied: tqdm in /usr/local/lib/python3.9/site-packages (from stexls==4.4.2) (4.54.0)
Requirement already satisfied: numpy in /usr/local/lib/python3.9/site-packages (from stexls==4.4.2) (1.19.4)
Collecting scikit-learn

  Downloading scikit_learn-0.24.1-cp39-cp39-macosx_10_13_x86_64.whl (7.3 MB)
     |████████████████████████████████| 7.3 MB 5.9 MB/s 
Collecting nltk
  Using cached nltk-3.5.zip (1.4 MB)
ERROR: Could not find a version that satisfies the requirement tensorflow (from stexls[ml])
ERROR: No matching distribution found for tensorflow

It seems that tensorflow is not available for python 3.9.
So I probably have to downgrade to python 3.8.