Added a warning about leastsq using with NaNs.
Added a warning about leastsq using with NaNs.

Added a warning that `func`'s retuned array_like must not contain NaNs or
computation might fail. Closes #3491

Eric89GXL/scipy,dominicelse/scipy,sriki18/scipy,rmcgibbo/scipy,giorgiop/scipy,nmayorov/scipy,mgaitan/scipy,vberaudi/scipy,jamestwebber/scipy,person142/scipy,arokem/scipy,Eric89GXL/scipy,e-q/scipy,FRidh/scipy,zxsted/scipy,anntzer/scipy,zxsted/scipy,jonycgn/scipy,jseabold/scipy,mtrbean/scipy,woodscn/scipy,niknow/scipy,aeklant/scipy,newemailjdm/scipy,jakevdp/scipy,mortonjt/scipy,hainm/scipy,andim/scipy,mdhaber/scipy,surhudm/scipy,mhogg/scipy,nvoron23/scipy,pbrod/scipy,ndchorley/scipy,woodscn/scipy,Srisai85/scipy,befelix/scipy,cpaulik/scipy,Srisai85/scipy,matthew-brett/scipy,jonycgn/scipy,mortada/scipy,Shaswat27/scipy,endolith/scipy,maniteja123/scipy,rmcgibbo/scipy,pnedunuri/scipy,gef756/scipy,ChanderG/scipy,ChanderG/scipy,trankmichael/scipy,ChanderG/scipy,lukauskas/scipy,kleskjr/scipy,Eric89GXL/scipy,maciejkula/scipy,witcxc/scipy,gfyoung/scipy,matthewalbani/scipy,felipebetancur/scipy,perimosocordiae/scipy,raoulbq/scipy,gertingold/scipy,josephcslater/scipy,lhilt/scipy,nonhermitian/scipy,aeklant/scipy,perimosocordiae/scipy,befelix/scipy,vanpact/scipy,andyfaff/scipy,ortylp/scipy,richardotis/scipy,WillieMaddox/scipy,pschella/scipy,piyush0609/scipy,giorgiop/scipy,haudren/scipy,ilayn/scipy,nvoron23/scipy,behzadnouri/scipy,woodscn/scipy,jjhelmus/scipy,sauliusl/scipy,aeklant/scipy,pbrod/scipy,nvoron23/scipy,hainm/scipy,sonnyhu/scipy,niknow/scipy,Shaswat27/scipy,richardotis/scipy,futurulus/scipy,mdhaber/scipy,Kamp9/scipy,gfyoung/scipy,larsmans/scipy,zxsted/scipy,WarrenWeckesser/scipy,ortylp/scipy,futurulus/scipy,rgommers/scipy,jakevdp/scipy,fredrikw/scipy,jsilter/scipy,mdhaber/scipy,mtrbean/scipy,pyramania/scipy,petebachant/scipy,bkendzior/scipy,mortonjt/scipy,felipebetancur/scipy,jakevdp/scipy,mikebenfield/scipy,person142/scipy,cpaulik/scipy,vhaasteren/scipy,jakevdp/scipy,rgommers/scipy,ortylp/scipy,aarchiba/scipy,vigna/scipy,sriki18/scipy,aeklant/scipy,pnedunuri/scipy,jonycgn/scipy,andyfaff/scipy,maciejkula/scipy,maniteja123/scipy,Shaswat27/scipy,zxsted/scipy,mingwpy/scipy,mortonjt/scipy,zerothi/scipy,jsilter/scipy,bkendzior/scipy,hainm/scipy,endolith/scipy,surhudm/scipy,vanpact/scipy,ales-erjavec/scipy,matthewalbani/scipy,Stefan-Endres/scipy,mikebenfield/scipy,fredrikw/scipy,futurulus/scipy,jor-/scipy,piyush0609/scipy,kleskjr/scipy,haudren/scipy,efiring/scipy,person142/scipy,FRidh/scipy,apbard/scipy,niknow/scipy,futurulus/scipy,argriffing/scipy,mhogg/scipy,sauliusl/scipy,newemailjdm/scipy,behzadnouri/scipy,mortonjt/scipy,mortada/scipy,njwilson23/scipy,vigna/scipy,woodscn/scipy,pschella/scipy,gef756/scipy,Dapid/scipy,Dapid/scipy,fredrikw/scipy,mtrbean/scipy,mtrbean/scipy,ndchorley/scipy,tylerjereddy/scipy,fredrikw/scipy,sriki18/scipy,kleskjr/scipy,argriffing/scipy,pbrod/scipy,chatcannon/scipy,jonycgn/scipy,sauliusl/scipy,mortada/scipy,anntzer/scipy,nonhermitian/scipy,ilayn/scipy,zerothi/scipy,petebachant/scipy,nvoron23/scipy,fredrikw/scipy,piyush0609/scipy,Gillu13/scipy,matthew-brett/scipy,maniteja123/scipy,mdhaber/scipy,chatcannon/scipy,Stefan-Endres/scipy,vberaudi/scipy,anielsen001/scipy,anielsen001/scipy,WarrenWeckesser/scipy,nvoron23/scipy,haudren/scipy,jsilter/scipy,Dapid/scipy,vanpact/scipy,dch312/scipy,mingwpy/scipy,Dapid/scipy,endolith/scipy,vhaasteren/scipy,mgaitan/scipy,surhudm/scipy,mgaitan/scipy,lhilt/scipy,ilayn/scipy,Stefan-Endres/scipy,efiring/scipy,gertingold/scipy,zerothi/scipy,endolith/scipy,gdooper/scipy,ales-erjavec/scipy,petebachant/scipy,niknow/scipy,jonycgn/scipy,ilayn/scipy,pbrod/scipy,sauliusl/scipy,mdhaber/scipy,Newman101/scipy,newemailjdm/scipy,ortylp/scipy,Stefan-Endres/scipy,dch312/scipy,kalvdans/scipy,surhudm/scipy,andyfaff/scipy,haudren/scipy,vberaudi/scipy,larsmans/scipy,hainm/scipy,anntzer/scipy,newemailjdm/scipy,pnedunuri/scipy,trankmichael/scipy,woodscn/scipy,sauliusl/scipy,trankmichael/scipy,sonnyhu/scipy,niknow/scipy,pnedunuri/scipy,andim/scipy,vanpact/scipy,Gillu13/scipy,aarchiba/scipy,petebachant/scipy,befelix/scipy,fernand/scipy,vberaudi/scipy,mhogg/scipy,arokem/scipy,behzadnouri/scipy,behzadnouri/scipy,rmcgibbo/scipy,Srisai85/scipy,jonycgn/scipy,aarchiba/scipy,scipy/scipy,fernand/scipy,felipebetancur/scipy,Kamp9/scipy,Shaswat27/scipy,vanpact/scipy,anntzer/scipy,e-q/scipy,sonnyhu/scipy,mhogg/scipy,vhaasteren/scipy,njwilson23/scipy,ilayn/scipy,ChanderG/scipy,sonnyhu/scipy,ortylp/scipy,maciejkula/scipy,giorgiop/scipy,mhogg/scipy,petebachant/scipy,sonnyhu/scipy,larsmans/scipy,Newman101/scipy,trankmichael/scipy,e-q/scipy,endolith/scipy,richardotis/scipy,nmayorov/scipy,scipy/scipy,argriffing/scipy,josephcslater/scipy,jamestwebber/scipy,Gillu13/scipy,WarrenWeckesser/scipy,mingwpy/scipy,zaxliu/scipy,anielsen001/scipy,sauliusl/scipy,pnedunuri/scipy,lukauskas/scipy,lukauskas/scipy,josephcslater/scipy,WillieMaddox/scipy,jjhelmus/scipy,bkendzior/scipy,jamestwebber/scipy,grlee77/scipy,gdooper/scipy,giorgiop/scipy,behzadnouri/scipy,andyfaff/scipy,gfyoung/scipy,jseabold/scipy,ales-erjavec/scipy,jjhelmus/scipy,josephcslater/scipy,haudren/scipy,mingwpy/scipy,matthew-brett/scipy,jakevdp/scipy,witcxc/scipy,njwilson23/scipy,matthew-brett/scipy,mortada/scipy,chatcannon/scipy,pschella/scipy,fernand/scipy,gdooper/scipy,lukauskas/scipy,zaxliu/scipy,lhilt/scipy,Srisai85/scipy,argriffing/scipy,niknow/scipy,maniteja123/scipy,minhlongdo/scipy,andim/scipy,felipebetancur/scipy,newemailjdm/scipy,njwilson23/scipy,e-q/scipy,jseabold/scipy,gertingold/scipy,Dapid/scipy,ndchorley/scipy,ales-erjavec/scipy,mortonjt/scipy,dch312/scipy,witcxc/scipy,aman-iitj/scipy,zerothi/scipy,zaxliu/scipy,tylerjereddy/scipy,Newman101/scipy,nonhermitian/scipy,kleskjr/scipy,vberaudi/scipy,Gillu13/scipy,WillieMaddox/scipy,jor-/scipy,Shaswat27/scipy,perimosocordiae/scipy,argriffing/scipy,perimosocordiae/scipy,fernand/scipy,minhlongdo/scipy,zerothi/scipy,cpaulik/scipy,efiring/scipy,vigna/scipy,piyush0609/scipy,matthewalbani/scipy,arokem/scipy,aarchiba/scipy,Kamp9/scipy,nvoron23/scipy,chatcannon/scipy,aman-iitj/scipy,haudren/scipy,endolith/scipy,mortonjt/scipy,jor-/scipy,giorgiop/scipy,raoulbq/scipy,Shaswat27/scipy,pyramania/scipy,e-q/scipy,zxsted/scipy,Gillu13/scipy,aman-iitj/scipy,aman-iitj/scipy,rmcgibbo/scipy,zaxliu/scipy,cpaulik/scipy,Kamp9/scipy,WillieMaddox/scipy,larsmans/scipy,gertingold/scipy,mgaitan/scipy,aarchiba/scipy,vhaasteren/scipy,ilayn/scipy,fernand/scipy,vigna/scipy,rgommers/scipy,ChanderG/scipy,matthewalbani/scipy,grlee77/scipy,Kamp9/scipy,zaxliu/scipy,futurulus/scipy,nmayorov/scipy,Kamp9/scipy,aeklant/scipy,dominicelse/scipy,gfyoung/scipy,trankmichael/scipy,kalvdans/scipy,apbard/scipy,woodscn/scipy,efiring/scipy,pizzathief/scipy,perimosocordiae/scipy,efiring/scipy,Dapid/scipy,scipy/scipy,dch312/scipy,cpaulik/scipy,dominicelse/scipy,Srisai85/scipy,gef756/scipy,aman-iitj/scipy,argriffing/scipy,petebachant/scipy,jsilter/scipy,raoulbq/scipy,sriki18/scipy,witcxc/scipy,trankmichael/scipy,minhlongdo/scipy,andim/scipy,gertingold/scipy,maniteja123/scipy,lukauskas/scipy,Newman101/scipy,Eric89GXL/scipy,giorgiop/scipy,pyramania/scipy,futurulus/scipy,Stefan-Endres/scipy,mhogg/scipy,andyfaff/scipy,WarrenWeckesser/scipy,jor-/scipy,sonnyhu/scipy,scipy/scipy,cpaulik/scipy,gef756/scipy,kalvdans/scipy,perimosocordiae/scipy,bkendzior/scipy,matthew-brett/scipy,jseabold/scipy,pschella/scipy,raoulbq/scipy,lukauskas/scipy,WarrenWeckesser/scipy,mgaitan/scipy,kalvdans/scipy,minhlongdo/scipy,ortylp/scipy,andim/scipy,jamestwebber/scipy,efiring/scipy,FRidh/scipy,surhudm/scipy,arokem/scipy,grlee77/scipy,chatcannon/scipy,pizzathief/scipy,minhlongdo/scipy,grlee77/scipy,pizzathief/scipy,kleskjr/scipy,anielsen001/scipy,vberaudi/scipy,gdooper/scipy,tylerjereddy/scipy,pbrod/scipy,vhaasteren/scipy,apbard/scipy,pizzathief/scipy,anntzer/scipy,jjhelmus/scipy,WillieMaddox/scipy,richardotis/scipy,Srisai85/scipy,Eric89GXL/scipy,larsmans/scipy,behzadnouri/scipy,ChanderG/scipy,Stefan-Endres/scipy,pnedunuri/scipy,dch312/scipy,jjhelmus/scipy,pschella/scipy,FRidh/scipy,gdooper/scipy,minhlongdo/scipy,nmayorov/scipy,scipy/scipy,mtrbean/scipy,maciejkula/scipy,arokem/scipy,jamestwebber/scipy,mtrbean/scipy,richardotis/scipy,mikebenfield/scipy,richardotis/scipy,scipy/scipy,ndchorley/scipy,sriki18/scipy,grlee77/scipy,felipebetancur/scipy,WarrenWeckesser/scipy,kleskjr/scipy,bkendzior/scipy,apbard/scipy,pyramania/scipy,kalvdans/scipy,surhudm/scipy,WillieMaddox/scipy,mingwpy/scipy,njwilson23/scipy,zxsted/scipy,raoulbq/scipy,fredrikw/scipy,vigna/scipy,hainm/scipy,jseabold/scipy,hainm/scipy,mgaitan/scipy,Eric89GXL/scipy,zaxliu/scipy,anielsen001/scipy,rmcgibbo/scipy,vhaasteren/scipy,gfyoung/scipy,mortada/scipy,josephcslater/scipy,mikebenfield/scipy,larsmans/scipy,person142/scipy,raoulbq/scipy,lhilt/scipy,Newman101/scipy,jseabold/scipy,andim/scipy,nonhermitian/scipy,rgommers/scipy,person142/scipy,lhilt/scipy,chatcannon/scipy,Newman101/scipy,Gillu13/scipy,tylerjereddy/scipy,aman-iitj/scipy,anielsen001/scipy,maniteja123/scipy,rgommers/scipy,witcxc/scipy,befelix/scipy,FRidh/scipy,ndchorley/scipy,apbard/scipy,newemailjdm/scipy,zerothi/scipy,dominicelse/scipy,mingwpy/scipy,mdhaber/scipy,fernand/scipy,piyush0609/scipy,pyramania/scipy,mikebenfield/scipy,dominicelse/scipy,FRidh/scipy,gef756/scipy,piyush0609/scipy,befelix/scipy,njwilson23/scipy,ales-erjavec/scipy,ales-erjavec/scipy,felipebetancur/scipy,maciejkula/scipy,andyfaff/scipy,jor-/scipy,nmayorov/scipy,gef756/scipy,pbrod/scipy,ndchorley/scipy,mortada/scipy,nonhermitian/scipy,pizzathief/scipy,matthewalbani/scipy,rmcgibbo/scipy,jsilter/scipy,anntzer/scipy,sriki18/scipy,vanpact/scipy,tylerjereddy/scipy