Fix issue #6127: Make universal newlines mode of io.StringIO not duplicate newlines under Windows (see also issue #5265 and #5645).
Fix issue #6127: Make universal newlines mode of io.StringIO not
duplicate newlines under Windows (see also issue #5265 and #5645).

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator