This is one of a series of bug reports / PRs that lay the groundwork for making pathlib extensible. See here for detail: https://discuss.python.org/t/make-pathlib-extensible/3428

Currently `_Accessor.open()` is expected to function like `os.open()` and return a file descriptor. I'd suggest this interface is too low-level if our eventual aim is to allow users to implement their own accessor.

It would be better is `_Accessor.open()` is expected to function like `io.open()` and return a file object. That way, accessors don't need to deal with file descriptors at all, which is important if they're working with remote filesystems.

I'm planning to wait for bpo-39895 / gh-18838 to land before starting work on this.

New changeset 11c3bd3f6d06649484b81a659c7bf02d6632e607 by Barney Gale in branch 'master':
bpo-40107: Switch to using io.open() for pathlib.Path.open() (GH-25240)
https://github.com/python/cpython/commit/11c3bd3f6d06649484b81a659c7bf02d6632e607