Python ports should follow its upstream naming (https://pypi.org/project/python-dateutil/). Please move devel/py-dateutil to devel/py-python-dateutil and bump dependet ports.
(In reply to Po-Chuan Hsieh from comment #0)
Forgot to mention the PORTNAME change.
Thanks for tracking this Sunpoet. Happy to review a diff if you'd like to take this. I wont have spare cycles for a while