install: handle FormulaClassUnavailableError
install: handle FormulaClassUnavailableError

Don't search for alternatives if formula was found, but has issues, as
this will create confusing output, particularly for contributors working
on a formula file.

mgrimes/brew,gregory-nisbet/brew,Homebrew/brew,jmsundar/brew,AnastasiaSulyagina/brew,aw1621107/brew,vitorgalvao/brew,JCount/brew,palxex/brew,reelsense/brew,reitermarkus/brew,nandub/brew,maxim-belkin/brew,muellermartin/dist,Linuxbrew/brew,ilovezfs/brew,sjackman/homebrew,aw1621107/brew,nandub/brew,bfontaine/brew,konqui/brew,DomT4/brew,muellermartin/dist,mahori/brew,maxim-belkin/brew,EricFromCanada/brew,pseudocody/brew,Linuxbrew/brew,EricFromCanada/brew,gregory-nisbet/brew,palxex/brew,amar-laksh/brew_sudo,MikeMcQuaid/brew,Homebrew/brew,hanxue/linuxbrew,konqui/brew,jmsundar/brew,mahori/brew,JCount/brew,vitorgalvao/brew,gordonmcshane/homebrew,reitermarkus/brew,pseudocody/brew,JCount/brew,claui/brew,pseudocody/brew,mistydemeo/homebrew,ilovezfs/brew,gordonmcshane/homebrew,nandub/brew,DomT4/brew,reelsense/brew,reelsense/brew,amar-laksh/brew_sudo,Homebrew/brew,staticfloat/brew,muellermartin/dist,ilovezfs/brew,hanxue/linuxbrew,tonyg/homebrew,mgrimes/brew,zmwangx/brew,tonyg/homebrew,JCount/brew,aw1621107/brew,AnastasiaSulyagina/brew,palxex/brew,DomT4/brew,hanxue/linuxbrew,mahori/brew,claui/brew,vitorgalvao/brew,Linuxbrew/brew,gordonmcshane/homebrew,vitorgalvao/brew,mistydemeo/homebrew,MikeMcQuaid/brew,gregory-nisbet/brew,amar-laksh/brew_sudo,EricFromCanada/brew,rwhogg/brew,Homebrew/brew,EricFromCanada/brew,zmwangx/brew,mgrimes/brew,toonetown/homebrew,konqui/brew,reitermarkus/brew,DomT4/brew,staticfloat/brew,rwhogg/brew,MikeMcQuaid/brew,MikeMcQuaid/brew,Linuxbrew/brew,sjackman/homebrew,zmwangx/brew,staticfloat/brew,bfontaine/brew,konqui/brew,sjackman/homebrew,rwhogg/brew,jmsundar/brew,tonyg/homebrew,nandub/brew,sjackman/homebrew,toonetown/homebrew,claui/brew,toonetown/homebrew,mistydemeo/homebrew,reitermarkus/brew,alyssais/brew,alyssais/brew,mahori/brew,alyssais/brew,AnastasiaSulyagina/brew,claui/brew,maxim-belkin/brew,bfontaine/brew