Opal 1.3 compatibility

hmdne · web-flow · commit c1c2a224dcfb · 2021-11-17T12:42:13.000+01:00
Only require IO::Writable if it's available - that is - before Opal 1.3
diff --git a/lib-opal/opal/rspec/formatter/document_io.rb b/lib-opal/opal/rspec/formatter/document_io.rb
@@ -1,7 +1,7 @@
 module Opal
   module RSpec
     class DocumentIO < IO
-      include IO::Writable
+      include IO::Writable if defined? IO::Writable
 
       def initialize
         `document.open()`
