ENH: Warn on unsupported Python 3.9+
ENH: Warn on unsupported Python 3.9+

grlee77/numpy,mattip/numpy,rgommers/numpy,mattip/numpy,charris/numpy,anntzer/numpy,simongibbons/numpy,jakirkham/numpy,rgommers/numpy,grlee77/numpy,pdebuyl/numpy,charris/numpy,endolith/numpy,pdebuyl/numpy,mhvk/numpy,seberg/numpy,mhvk/numpy,mhvk/numpy,simongibbons/numpy,grlee77/numpy,numpy/numpy,charris/numpy,madphysicist/numpy,mattip/numpy,rgommers/numpy,pbrod/numpy,mhvk/numpy,simongibbons/numpy,pbrod/numpy,numpy/numpy,pbrod/numpy,rgommers/numpy,seberg/numpy,jakirkham/numpy,mhvk/numpy,pbrod/numpy,charris/numpy,simongibbons/numpy,anntzer/numpy,mattip/numpy,anntzer/numpy,jakirkham/numpy,pdebuyl/numpy,jakirkham/numpy,pdebuyl/numpy,endolith/numpy,simongibbons/numpy,numpy/numpy,madphysicist/numpy,anntzer/numpy,numpy/numpy,madphysicist/numpy,madphysicist/numpy,seberg/numpy,jakirkham/numpy,grlee77/numpy,grlee77/numpy,pbrod/numpy,endolith/numpy,madphysicist/numpy,seberg/numpy,endolith/numpy