[rubygems/rubygems] Restore ability to load old marshalled gemspec that use `YAML::PrivateType`

This issue was not detected because when all traces of old YAML parser
and emitter `Syck` were removed, this null-type.gemspec.rz marshalled
gemspec was updated to no longer load `YAML::Syck::PrivateType` but load
`Psych::PrivateType` instead.

However, realworld old marshalled gemspecs still use the
`YAML::PrivateType` constant, so this commit replaces the gemspec to be
the real pry-0.4.7 marshalled gemspec, so that it catches this issue.

https://github.com/rubygems/rubygems/commit/51b330b8d2

2 files changed, 8 insertions, 1 deletions

diff --git a/lib/rubygems/specification.rb b/lib/rubygems/specification.rb
index aaf11ebd98..b0045ba511 100644
--- a/lib/rubygems/specification.rb
+++ b/lib/rubygems/specification.rb
@@ -1270,7 +1270,14 @@ class Gem::Specification < Gem::BasicSpecification
   def self._load(str)
     Gem.load_yaml
 
-    array = Marshal.load str
+    array = begin
+      Marshal.load str
+    rescue ArgumentError => e
+      raise unless e.message.include?("YAML")
+
+      Object.const_set "YAML", Psych
+      Marshal.load str
+    end
 
     spec = Gem::Specification.new
     spec.instance_variable_set :@specification_version, array[1]
diff --git a/test/rubygems/data/null-type.gemspec.rz b/test/rubygems/data/null-type.gemspec.rz
index 2134fcde29..58fc1ed8a0 100644
--- a/test/rubygems/data/null-type.gemspec.rz
+++ b/test/rubygems/data/null-type.gemspec.rz