[ruby-core:67882] Regex :blank: behavior changed with Ruby 2.2

The following RubySpec is passing on 2.0 and 2.1 but failing on 2.2 and
2.3.  Is this new behavior correct or should a bug be reported?

https://github.com/anthonycrumley/rubyspec/blob/master/language/regexp/char=
acter_classes_spec.rb#L145

1)
Regexp with character classes matches Unicode space characters with
[[:blank:]] FAILED
Expected []
 to equal ["=E1=A0=8E"]

/vagrant/spec/rubyspec/language/regexp/character_classes_spec.rb:145:in
`block (2 levels) in <top (required)>'
/vagrant/spec/rubyspec/language/regexp/character_classes_spec.rb:4:in `<top
(required)>'