Fix relativity.py to work correctly with dsolve
Fix relativity.py to work correctly with dsolve

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