Fixes #9135

Failing at the moment, because Python 2 open() doesn't have an encoding argument 🙁

Let's leave this till we remove Python 2 tests.

io.open should work in all versions I think

Yeah, probably. But I don't see the point if we're likely to rip it out in a couple of months. I'm happy if someone else wants to make this Python 2 compatible, though.

How do you feel about waiting a couple of weeks, and then we'll revisit this, because master won't be Python 2?

This is also related to #9054 (which I believe would also be resolved by this fix). io.open() returns unicode on Python 2, but pip uses str all over the place. Switching to it would cause a cascade of unicode coersion issues elsewhere, and likely break things that rely on platform-specific encoding (and are currently working). I agree with Paul this should not be backported to Python 2.

OTOH I really would like this to be fixed for Python 3 before we drop Python 2, otherwise there would be no migration path available for people stuck on Python 2 due to this issue (may be a hypothetical problem at this point though). Maybe we can do something like

if six.PY2:
    f = open(...)
else:
    f = open(..., encoding="utf8")
with f:
    f.write(...)

@uranusjr I have no objection if you want to make a version of this fix that supports Python 2, but I don't expect to do so myself.

This is also related to #9054

Ah yes, I knew I remembered this issue having come up recently, but I couldn't find it. Thanks for the link.

Was there a reason this was closed? The issue still seems to be present.

IIRC this was abandoned because Python 2 was too difficult to handle. Since that is no longer an issue, feel free to submit a new PR.