Prepend cask name to cask upgrade error message

[kiendang]

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When upgrading casks all exceptions are aggregated and displayed at the end. When multiple casks are upgraded, this makes it sometimes not obvious which cask the exception belongs to.

Solution: prepend the cask name to the error message.

Before

Error: pkg source file not found: 'gfortran-6.3-Sierra/gfortran.pkg'

After

Error: gfortran 6.3: pkg source file not found: 'gfortran-6.3-Sierra/gfortran.pkg'

(In this example the original error message contains gfortran. However in some cases the error message does not contain reference to the cask being upgraded at all.)

[vitorgalvao]

I’m fine with it, though please remove the version from the message. It’s not particularly useful information and will make it harder to understand which cask it is, because it becomes ambiguous if it’s from homebrew/cask-versions or another repo.

[MikeMcQuaid]

Thanks again @kiendang!