Add line break to string

Library/Homebrew/cask/lib/hbc/cli/internal_stanza.rb

@@ -46,8 +46,10 @@ module Hbc
 
         return if DSL::DSL_METHODS.include?(stanza)
         raise ArgumentError,
-          "Unknown/unsupported stanza: '#{stanza}' Check cask reference"\
-          " for supported stanzas."
+          <<~EOS
+            Unknown/unsupported stanza: '#{stanza}'
+            Check cask reference for supported stanzas.
+          EOS
       end
 
       def run

Library/Homebrew/test/cask/cli/internal_stanza_spec.rb

@@ -9,7 +9,7 @@ describe Hbc::CLI::InternalStanza, :cask do
   it "raises an exception when stanza is unknown/unsupported" do
     expect {
       described_class.new("this_stanza_does_not_exist", "with-gpg")
-    }.to raise_error(/Unknown\/unsupported stanza/)
+    }.to raise_error(%r{Unknown/unsupported stanza})
   end
 
   it "raises an exception when normal stanza is not present on cask" do