Merge pull request #2263 from reitermarkus/spec-cmd-cask

Silence `cmd/cask` test.

Library/Homebrew/test/cmd/cask_spec.rb

@@ -2,7 +2,9 @@ describe "brew cask", :integration_test, :needs_macos, :needs_official_cmd_taps
   describe "list" do
     it "returns a list of installed Casks" do
       setup_remote_tap("caskroom/cask")
-      expect { brew "cask", "list" }.to be_a_success
+      shutup do
+        expect { brew "cask", "list" }.to be_a_success
+      end
     end
   end
 end