DefaultProvider.get_resource_stream in pkg_resources should use io.open instead of open on Python 2 for multiple reasons:

• better compatibility with python 3 code. On Python 3 open == io.open
• better compatibility between the providers. The NullProvider uses io.BytesIO which has the same interface as io.open
• allows using wrappers like TextIOWrapper which can then be used to convert the binary stream to a text stream.