utilities/source: remove encode to 'ascii'
utilities/source: remove encode to 'ascii'

In utilities/source, we tried to optimize function name lookup by
encoding to 'ascii' (as an unicode string can't be a function name). This
fails in Python 3 because all strings are unicode. Fix by removing the
encode.

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