Fix set_sort_fn in sets.py.
Fix set_sort_fn in sets.py.

This makes set_sort_fn independent of hashes and also solves the issue
with S.EmptySet | FiniteSet(x, FiniteSet(y, z)).

madan96/sympy,lindsayad/sympy,wanglongqi/sympy,shikil/sympy,Sumith1896/sympy,abloomston/sympy,beni55/sympy,meghana1995/sympy,Curious72/sympy,Mitchkoens/sympy,farhaanbukhsh/sympy,kmacinnis/sympy,ChristinaZografou/sympy,drufat/sympy,souravsingh/sympy,kevalds51/sympy,asm666/sympy,abhiii5459/sympy,saurabhjn76/sympy,postvakje/sympy,ahhda/sympy,kaichogami/sympy,abhiii5459/sympy,pbrady/sympy,maniteja123/sympy,atsao72/sympy,bukzor/sympy,kaichogami/sympy,AkademieOlympia/sympy,toolforger/sympy,Vishluck/sympy,debugger22/sympy,farhaanbukhsh/sympy,debugger22/sympy,emon10005/sympy,kaushik94/sympy,srjoglekar246/sympy,jbbskinny/sympy,skidzo/sympy,dqnykamp/sympy,emon10005/sympy,postvakje/sympy,emon10005/sympy,kumarkrishna/sympy,Shaswat27/sympy,Designist/sympy,Arafatk/sympy,iamutkarshtiwari/sympy,aktech/sympy,hrashk/sympy,sahmed95/sympy,grevutiu-gabriel/sympy,sampadsaha5/sympy,garvitr/sympy,jaimahajan1997/sympy,kaushik94/sympy,jerli/sympy,shipci/sympy,cccfran/sympy,MechCoder/sympy,abloomston/sympy,debugger22/sympy,postvakje/sympy,Titan-C/sympy,Titan-C/sympy,shikil/sympy,Vishluck/sympy,hargup/sympy,Gadal/sympy,atsao72/sympy,jaimahajan1997/sympy,meghana1995/sympy,cccfran/sympy,shipci/sympy,maniteja123/sympy,chaffra/sympy,asm666/sympy,grevutiu-gabriel/sympy,sunny94/temp,drufat/sympy,yashsharan/sympy,saurabhjn76/sympy,jamesblunt/sympy,toolforger/sympy,ChristinaZografou/sympy,sahmed95/sympy,hargup/sympy,Sumith1896/sympy,lidavidm/sympy,wanglongqi/sympy,ga7g08/sympy,lidavidm/sympy,Arafatk/sympy,Gadal/sympy,sampadsaha5/sympy,kaushik94/sympy,rahuldan/sympy,wyom/sympy,bukzor/sympy,kmacinnis/sympy,ga7g08/sympy,sahilshekhawat/sympy,sahilshekhawat/sympy,shipci/sympy,skidzo/sympy,farhaanbukhsh/sympy,vipulroxx/sympy,wyom/sympy,MridulS/sympy,liangjiaxing/sympy,sunny94/temp,Vishluck/sympy,pbrady/sympy,oliverlee/sympy,lindsayad/sympy,Curious72/sympy,oliverlee/sympy,meghana1995/sympy,flacjacket/sympy,mcdaniel67/sympy,jbbskinny/sympy,shikil/sympy,toolforger/sympy,jbbskinny/sympy,yukoba/sympy,abhiii5459/sympy,wyom/sympy,cswiercz/sympy,Davidjohnwilson/sympy,souravsingh/sympy,atreyv/sympy,Davidjohnwilson/sympy,hrashk/sympy,moble/sympy,kevalds51/sympy,liangjiaxing/sympy,kmacinnis/sympy,AkademieOlympia/sympy,cswiercz/sympy,oliverlee/sympy,VaibhavAgarwalVA/sympy,garvitr/sympy,dqnykamp/sympy,MridulS/sympy,mafiya69/sympy,garvitr/sympy,kaichogami/sympy,diofant/diofant,yukoba/sympy,MechCoder/sympy,aktech/sympy,mafiya69/sympy,jerli/sympy,iamutkarshtiwari/sympy,ChristinaZografou/sympy,skirpichev/omg,moble/sympy,MechCoder/sympy,moble/sympy,yashsharan/sympy,madan96/sympy,sahmed95/sympy,asm666/sympy,Gadal/sympy,VaibhavAgarwalVA/sympy,hargup/sympy,sampadsaha5/sympy,mcdaniel67/sympy,AunShiLord/sympy,beni55/sympy,iamutkarshtiwari/sympy,yashsharan/sympy,cswiercz/sympy,ahhda/sympy,kumarkrishna/sympy,pbrady/sympy,pandeyadarsh/sympy,jamesblunt/sympy,lindsayad/sympy,hrashk/sympy,Designist/sympy,jerli/sympy,Shaswat27/sympy,souravsingh/sympy,chaffra/sympy,Arafatk/sympy,MridulS/sympy,atreyv/sympy,cccfran/sympy,jamesblunt/sympy,kevalds51/sympy,aktech/sympy,grevutiu-gabriel/sympy,ga7g08/sympy,saurabhjn76/sympy,rahuldan/sympy,yukoba/sympy,dqnykamp/sympy,ahhda/sympy,Curious72/sympy,amitjamadagni/sympy,abloomston/sympy,VaibhavAgarwalVA/sympy,maniteja123/sympy,Titan-C/sympy,amitjamadagni/sympy,Mitchkoens/sympy,vipulroxx/sympy,chaffra/sympy,Designist/sympy,jaimahajan1997/sympy,beni55/sympy,sunny94/temp,liangjiaxing/sympy,atsao72/sympy,AunShiLord/sympy,bukzor/sympy,rahuldan/sympy,mafiya69/sympy,mcdaniel67/sympy,Davidjohnwilson/sympy,pandeyadarsh/sympy,Sumith1896/sympy,Mitchkoens/sympy,Shaswat27/sympy,drufat/sympy,vipulroxx/sympy,lidavidm/sympy,sahilshekhawat/sympy,AkademieOlympia/sympy,wanglongqi/sympy,atreyv/sympy,AunShiLord/sympy,skidzo/sympy,kumarkrishna/sympy,madan96/sympy,pandeyadarsh/sympy