Refactor Cask exceptions.

Library/Homebrew/cask/lib/hbc/cask_loader.rb

Library/Homebrew/cask/lib/hbc/cli.rb

Library/Homebrew/cask/lib/hbc/cli/edit.rb

Library/Homebrew/cask/lib/hbc/cli/install.rb

Library/Homebrew/cask/lib/hbc/cli/reinstall.rb

Library/Homebrew/cask/lib/hbc/exceptions.rb

Library/Homebrew/cask/lib/hbc/installer.rb

Library/Homebrew/cask/lib/hbc/verify/checksum.rb

Library/Homebrew/test/cask/cli/install_spec.rb

Library/Homebrew/test/cask/dsl_spec.rb

Library/Homebrew/test/cask/installer_spec.rb

Library/Homebrew/test/cask/verify/checksum_spec.rb