bpo-35128: Fix spacing issues in warning.warn messages

[scorphus]

Some warn messages miss space between words, such as:

Use of 'buffering' argument is deprecated  and ignoredsince Python 3.0.

in bz2 library, and:

keyfile and certfile are deprecated, use acustom context instead

in many libraries, such as poplib and smtplib.

Other warn messages contain too much spaces between words, such as:

The 'filename' attribute will be removed in future versions.  Use 'source' instead.

in configparser library.

As "Trivial changes, like fixing a typo, do not need an issue", I closed the one I had previously opened (issue35128)

https://bugs.python.org/issue35128

[daniellovell]

Hi @scorphus, to address some of the errored and failing checks you're receiving, I'd recommend putting the Python BPO issue number in the title of your PR as detailed in the devguide.

e.g. "bpo-35128: Fix spacing issues in warning.warn messages"

[serhiy-storchaka]

Double space after a period is not a bug.

[ezio-melotti]

Double spaces after the "." are intentional and should be kept, the others are bugs and should be fixed.

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[scorphus]

Agreed on the double spaces as they increase readability (of the messages) 👍

Should I include a news entry or are you going to add that label?

Thanks a lot for reviewing!!

[scorphus]

Great! Can I help backporting!?

[miss-islington]

Thanks @scorphus for the PR, and @serhiy-storchaka for merging it 🌮🎉.. I'm working now to backport this PR to: 3.6, 3.7.
🐍🍒⛏🤖

[miss-islington]

Sorry, @scorphus and @serhiy-storchaka, I could not cleanly backport this to 3.7 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 4b5e62dbb22a3593e0db266c12f805b727a42b00 3.7

[miss-islington]

Sorry, @scorphus and @serhiy-storchaka, I could not cleanly backport this to 3.6 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 4b5e62dbb22a3593e0db266c12f805b727a42b00 3.6

[bedevere-bot]

GH-10280 is a backport of this pull request to the 3.7 branch.

[bedevere-bot]

GH-10281 is a backport of this pull request to the 3.6 branch.