Check macos version before download

[brandonkal]

Description of feature/enhancement

Having an app download and then not be installed because of a depends_on clause that specifies a different OS version is not the best experience. Ideally, Homebrew should validate the OS version requirements first before attempting to download a cask.

Justification

See above

Example use case

See the calibre cask. The dmg is downloaded on my slow connection and then home-brew reports that mojave is required. The experience could be worse for larger applications.

[grantfar]

I will take this

[vitorgalvao]

Thank you, @grantfar. We’ll be awaiting the PR. If you have any specific questions, let us know.

[Akylzhan]

@vitorgalvao I was thinking about this problem a bit
What if we will change the order in installer.rb to this:

satisfy_dependencies
verify_has_sha if require_sha? && !force?
download
verify

[vitorgalvao]

It probably should be above just above download, but yes, that seems like it might work.