GPG container contain file content and signature and thus don't have or need *.asc files

e.g.

url "https://server.com/package.gpg"
gpg :embedded, key_url: 'https://keys.org/package.pub'

Library/Homebrew/cask/lib/hbc/dsl/gpg.rb

@@ -14,7 +14,7 @@ module Hbc
 
       def initialize(signature, parameters = {})
         @parameters = parameters
-        @signature = URI(signature)
+        @signature = URI(signature) unless signature == :embedded
         parameters.each do |hkey, hvalue|
           raise "invalid 'gpg' parameter: '#{hkey.inspect}'" unless VALID_PARAMETERS.include?(hkey)
           writer_method = "#{hkey}=".to_sym