Make capsys more like stdio streams in python3. Resolves #1407.

[asottile]

Replay of #2265 against origin/features

[coveralls]

Coverage increased (+0.04%) to 92.772% when pulling 4b2ca16 on asottile:capture_v2 into 44ad369 on pytest-dev:features.

[asottile]

See discussion in #2265

[nicoddemus]

I would rather at this point to be explicit about the expected behavior in Python 3:

@pytest.mark.skipif(sys.version_info[0] == 2, 'python 3 only behavior')
def test_write_bytes_to_buffer(self):
    """In python3, stdout / stderr are text io wrappers (exposing a buffer
    property of the underlying bytestream). See issue #1407
    """
    f = capture.CaptureIO()
    f.buffer.write(b'foo\r\n')
    assert f.getvalue() == 'foo\n'

(I also added a \r\n there to ensure we are not messing with how newlines are treated)

[asottile]

Done!

[nicoddemus]

Thanks for following up @asottile!

Looking over at #1407, I noticed this comment from @RonnyPfannschmidt. @RonnyPfannschmidt you still think the same way?

[coveralls]

Coverage increased (+0.04%) to 92.772% when pulling 8b598f0 on asottile:capture_v2 into 44ad369 on pytest-dev:features.

[asottile]

Looks like travis-ci is only failing due to the nightly

[nicoddemus]

Yes, and the same failures are happening on master for the nightly job. The AppVeyor failure seemed to be a fluke of the CI, I have triggered it again.

[RonnyPfannschmidt]

@nicoddemus i still think the capture objects should be simple/simplified, but since we have no way to properly do any cases, this pr adds value in any case

[nicoddemus]

Thanks @RonnyPfannschmidt, merging it then.

Thanks @asottile again for the contribution!