Please resolve conflicts and add tests. Also capitalize the first letter of a sentence in a NEWS entry.

@serhiy-storchaka Conflicts resolved & NEWS entry edited. I'm wondering if I need to open another PR for the tests or just add them in this one.

It is better to add new tests in the same PR. It makes easier to check that they fail without this change and pass with it.

I've added a simple test case and I found that the test case would fail the C implementation. Since I'm unfamiliar with the C code, might need some help from others to modify the C code.
BTW, not pretty clear on the implementation differences, is it okay that the error-raising logic varies between them?

It is more complex issue than covered in this PR. If change the behavior of text file read() for non-blocking buffered readers, the same change should be done for non-blocking raw files. If change the behavior for "read-until-end", the same change should be done for partial read.

And of course the behavior of both C and Python implementation should be consistent.

Thank you for reviving this issue, I will look what can I do with this.