title: brew cask Update or uninstall error: definition is invalid: invalid 'depends_on macos' value: ":lion"
body: <p>I can't uninstall or upgrade some casks due to a definition error.</p>
  
  <p>F.e. if I run update or upgrade:</p>
  
  <pre><code>brew cask upgrade the-unarchiver  
  Error: Cask 'the-unarchiver' definition is invalid: invalid 'depends_on macos' value: ":lion"
  
  brew cask uninstall the-unarchiver 
  Error: Cask 'the-unarchiver' definition is invalid: invalid 'depends_on macos' value: ":lion"
  </code></pre>
  
  <p>I've tried to see if there's something I can edit in the formula but I didn't find anything related to this error.</p>
  
  <pre><code>cask 'the-unarchiver' do
    version '4.1.0,121:1549634528'
    sha256 'ff97b168f07d084e88f48e5d1e5202445596acd6eec39685d28910ee71d3a74b'
  
    # devmate.com/com.macpaw.site.theunarchiver was verified as official when first introduced to the cask
    url "https://dl.devmate.com/com.macpaw.site.theunarchiver/#{version.after_comma.before_colon}/#{version.after_colon}/TheUnarchiver-#{version.after_comma.before_colon}.zip"
    appcast 'https://updates.devmate.com/com.macpaw.site.theunarchiver.xml'
    name 'The Unarchiver'
    homepage 'https://theunarchiver.com/'
  
    auto_updates true
  
    app 'The Unarchiver.app'
  
    zap trash: [
                 '~/Library/Caches/cx.c3.theunarchiver',
                 '~/Library/Cookies/cx.c3.theunarchiver.binarycookies',
                 '~/Library/Preferences/cx.c3.theunarchiver.plist',
                 '~/Library/Saved Application State/cx.c3.theunarchiver.savedState',
               ]
  end
  </code></pre>