Add missing file

lib/rubygems/syck_hack.rb

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+# :stopdoc:
+
+# Hack to handle syck's DefaultKey bug
+#
+# This file is always loaded AFTER either syck or psych are already
+# loaded. It then looks at what constants are available and creates
+# a consistent view on all rubys.
+#
+# All this is so that there is always a YAML::Syck::DefaultKey
+# class no matter if the full yaml library has loaded or not.
+#
+
+module YAML
+  # In newer 1.9.2, there is a Syck toplevel constant instead of it
+  # being underneith YAML. If so, reference it back under YAML as
+  # well.
+  if defined? ::Syck
+    Syck = ::Syck
+
+  # Otherwise, if there is no YAML::Syck, then we've got just psych
+  # loaded, so lets define a stub for DefaultKey.
+  elsif !defined? YAML::Syck
+    module Syck
+      class DefaultKey
+      end
+    end
+  end
+
+  # Now that we've got something that is always here, define #to_s
+  # so when code tries to use this, it at least just shows up like it
+  # should.
+  module Syck
+    class DefaultKey
+      def to_s
+        '='
+      end
+    end
+  end
+end
+
+# Sometime in the 1.9 dev cycle, the Syck constant was moved from under YAML
+# to be a toplevel constant. So gemspecs created under these versions of Syck
+# will have references to Syck::DefaultKey.
+#
+# So we need to be sure that we reference Syck at the toplevel too so that
+# we can always load these kind of gemspecs.
+#
+if !defined?(Syck)
+  Syck = YAML::Syck
+end
+
+# :startdoc: