Space after keyword optional arguments is not enforced

[owst]

Consider:

def f(x:1)
  { x:x }
end

Rubocop (0.36.0 (using Parser 2.3.0.7, running on ruby 2.2.0 x86_64-darwin14)) says only:

Offenses:

/tmp/foo.rb:2:6: C: Space missing after colon.
  { x:x }
     ^

1 file inspected, 1 offense detected

Which seems inconsistent; I think the keyword optional argument should also require a space after the colon.