pretty_symbology: Don't assume the output of U() is not None
pretty_symbology: Don't assume the output of U() is not None

U() returns None when unicodedata can't be imported. I'm not sure how to test
this because it's only reproducible if unicodedata from the standard library
can't be imported.  I suppose we could add a hook to test it. It won't be
straight-forward though because the key thing is to make sure it works
correctly at import time.

Fixes #8163.

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