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
8381c568e7