Termux upgrade fails: can't find archive

Today I installed visidata: $ pip3 install visidata as a dependency python-dateutil was also installed in the process. Afterwards, I wanted to upgrade the termux packages: $ pkg upgrade But now this does not work any more. “E: The package python3-dateutil needs to be reinstalled, but I can’t find an archive for it.” I get error messages like that. Deinstalling python-dateutil and visidata did not help either. I am getting basically the same error when using $ apt upgrade which I would usually use. What can I do to get that working again - preferably with visidata?