TST: Improve a number of mypy-related exception messages
TST: Improve a number of mypy-related exception messages

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