diagnostic: report unreadable, installed formulae.
diagnostic: report unreadable, installed formulae.

We previously did this somewhat unintentionally. `brew readall` does
this for all formulae but takes way longer.

vitorgalvao/brew,claui/brew,claui/brew,reitermarkus/brew,vitorgalvao/brew,mahori/brew,Homebrew/brew,MikeMcQuaid/brew,JCount/brew,reitermarkus/brew,mahori/brew,vitorgalvao/brew,mahori/brew,konqui/brew,nandub/brew,sjackman/homebrew,JCount/brew,nandub/brew,nandub/brew,konqui/brew,sjackman/homebrew,reitermarkus/brew,reitermarkus/brew,konqui/brew,Homebrew/brew,EricFromCanada/brew,MikeMcQuaid/brew,claui/brew,konqui/brew,EricFromCanada/brew,Homebrew/brew,sjackman/homebrew,MikeMcQuaid/brew,vitorgalvao/brew,JCount/brew,JCount/brew,sjackman/homebrew,mahori/brew,nandub/brew,MikeMcQuaid/brew,EricFromCanada/brew,claui/brew,Homebrew/brew,EricFromCanada/brew