MAINT: changed vague exception messages to a more descriptive ones that accurately reflect the condition. (#15728)
MAINT: changed vague exception messages to a more descriptive ones that accurately reflect the condition. (#15728)

* added more descriptive exception messages

* MAINT: changed exception message format
ilayn/scipy,perimosocordiae/scipy,Stefan-Endres/scipy,vigna/scipy,mdhaber/scipy,Stefan-Endres/scipy,WarrenWeckesser/scipy,scipy/scipy,andyfaff/scipy,scipy/scipy,endolith/scipy,anntzer/scipy,rgommers/scipy,endolith/scipy,scipy/scipy,endolith/scipy,WarrenWeckesser/scipy,mdhaber/scipy,endolith/scipy,mdhaber/scipy,andyfaff/scipy,perimosocordiae/scipy,ilayn/scipy,Stefan-Endres/scipy,mdhaber/scipy,scipy/scipy,anntzer/scipy,endolith/scipy,perimosocordiae/scipy,WarrenWeckesser/scipy,anntzer/scipy,andyfaff/scipy,Stefan-Endres/scipy,scipy/scipy,rgommers/scipy,WarrenWeckesser/scipy,Stefan-Endres/scipy,ilayn/scipy,mdhaber/scipy,rgommers/scipy,ilayn/scipy,vigna/scipy,vigna/scipy,WarrenWeckesser/scipy,andyfaff/scipy,mdhaber/scipy,ilayn/scipy,scipy/scipy,perimosocordiae/scipy,andyfaff/scipy,anntzer/scipy,WarrenWeckesser/scipy,Stefan-Endres/scipy,rgommers/scipy,rgommers/scipy,perimosocordiae/scipy,endolith/scipy,perimosocordiae/scipy,ilayn/scipy,anntzer/scipy,andyfaff/scipy,vigna/scipy,vigna/scipy,anntzer/scipy