I did nothing. Why does it think I did something?@hugovk or@AlexWaygood can you explain?

It looks like you made this PR directly from yourmain branch. That's generally a bad idea — it can cause strange things like this to happen :)

I suggest always making a new branch for each PR you create on github

What I've been doing with these small edits is to edit the file onpython/cpython in GitHub. I guess I accidentally edited this one onsmontanaro/cpython.

I find the whole manually create a new branch for each little change to be annoying, so for these small edits I've resorted to editing through the GitHub web interface. (I actually edit locally, remakehtml orhtmllive, then check the result and paste the edited file into the web interface.)

Specifically, it looks like you might have force-pushed to themain branch of your CPython clone to get it in sync with CPython'smain branch. That then meant that there were 0 changes between yourmain branch and CPython'smain branch; so, since this is a PR asking for changes from yourmain branch to be merged into CPython'smain branch, github automatically closed the PR.

Okay, I can buy that. I do remember accidentally committing some small doc change, then later issuing agit revert command.