Use io.open to open streams in PackageResource.open for filesystem resources
Use io.open to open streams in PackageResource.open for filesystem resources

It seems the default filestream opened by pkg_resources.resource_stream
is not always usable for TextIOWrapper, even if a file resource is
opened.

pymad/jpymad,pymad/cpymad,pymad/jpymad,pymad/jpymad,pymad/cpymad