Sorry, I misinterpreted your comments and consequently thought that `io.open` behaves differently on python{2,3}. As this is not the case, I'm okay with the change.

Still, I disagree with your reasoning (that is, if I'm understanding you correctly). As developers, we must keep in mind the defaults of some python functions, and then overwrite these to ensure consistency in our applications. IMO, all platform specific defaults that do not act as normalizations between platforms MUST be overwritten. This simplifies usage in user code and documentation as well.
Using `io.open` is an implementation detail. No user should need to read the source code to know what to expect from the behaviour of the application.