Fix py3.12 warnings for datetime usage, non-raw regex strings

[smemsh]

After upgrading my python3 from python-3.9 to python-3.12, running the test target causes a bunch of new warnings to be emitted. These are regarding datetime.datetime.utcnow() being deprecated. This is because upstream wants to make changes to naive datetimes (those without tzdata).

Here is the blurb from https://docs.python.org/3/whatsnew/3.12.html:

datetime: datetime.datetime’s utcnow() and utcfromtimestamp() are deprecated and will be removed in a future version. Instead, use timezone-aware objects to represent datetimes in UTC: respectively, call now() and fromtimestamp() with the tz parameter set to datetime.UTC.

There is some discussion of upstream's rationale in python/cpython#81669.

For the fix, I chose to use datetime.timezone.utc rather than datetime.UTC because the latter was only added in python-3.11 and I wanted the tests to work under both python-3.9 and python-3.12.

The following edit sequences were run to produce the changes:

First, test_totals.t had imported all of datetime, unlike all the other files which were importing individual names from datetime. It also did a wildcard import from ext/totals.py which caused a shadowing issue so I made the imports more specific. Now taht file imports datetime like the others, so later mass-edits (below) will work on this file too:

sed -i \
-e 's/^.*totals.*\*/from totals import format_seconds, calculate_totals/' \
-e 's/^import.datetime$/from datetime import datetime, timedelta/' \
-e 's/datetime\.datetime\./datetime./g' \
-e 's/datetime\.timedelta/timedelta/' \
test/test_totals.t

Next, we replace the deprecated utcnow() with a tzinfo-aware call, which can be done directly by giving a zone argument to now() but in other uses, a tzinfo-naive object is obtained, used for some things, and then later its .utcnow() method is run. We had to convert those uses in-place by first localizing:

grep -lsrF \
  -e 'datetime.now().utcnow()' \
  -e 'now.utcnow()' \
| xargs sed -i \
  -e 's/datetime.now().utcnow()/datetime.now(timezone.utc)/g' \
  -e '/import.datetime/a\' \
  -e 'from dateutil import tz' \
  -e 's/^\(from datetime import datetime,\)/\1 timezone,/' \
  -e 's/now.utcnow()/now.replace(tzinfo=tz.tzlocal()).astimezone(timezone.utc)/'

Finally, I removed the tzlocal import from files that didn't need it because they didn't do a conversion from naive objects to a aware objects (in the transform above):

for file in $(grep -lsr 'from.dateutil.import.tz$' test)
do grep -q tzlocal $file || sed -i '/^from.dateutil.import.tz$/d' $file
done

Incidentally, there were some regexes in summary.t that are not raw-quoted, generating a warning on embedded \d in non-raw quoted strings. These were probably already warnings before. They were fixed en passant in a separate commit.

Please apply, thanks.

[lauft]

Thanks ❤️