Remove pytz dependency, require Python 3.9+, extend tests

[do3cc]

This is the PR to implement #42
I've reviewed timezone/utils.py and noticed a lot of code isn´t used at all.
Then I added tests for windows and macos to make sure, nothing breaks.
Since nothing broke, I got worried and extended the tests to use timezones as provided by Python 3.9.
Then my windows tests failed and I added the necessary dependency for windows.
Now that I am writing this, I am wondering whether we should depend on tzinfo, for windows, as we don´t use the available timezones anywhere. However, I like that there are tests for that.

[justinmayer]

Thanks for your work on this, Patrick.

@venthur / @hugovk: I am preparing for a trip and could use an extra pair of eyes. Would you mind taking a look and providing any feedback you may have?

[do3cc]

After this I also downloaded pelican and made a test run with my modified branch. No failures. However I saw a few skipped tests due to missing locales.

[hugovk]

Also:

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 5b811c0..d2d7027 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,7 +1,7 @@
 ---
 repos:
   - repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v4.6.0
+    rev: v5.0.0
     hooks:
       - id: check-added-large-files
       - id: check-ast
@@ -15,7 +15,7 @@ repos:
       - id: trailing-whitespace
 
   - repo: https://github.com/asottile/pyupgrade
-    rev: v3.15.2
+    rev: v3.19.1
     hooks:
       - id: pyupgrade
-        args: [--py38-plus]
+        args: [--py39-plus]

[do3cc]

Everything addressed. Thanks for the review

[venthur]

Thanks for your contribution and addressing all requests @do3cc! @justinmayer the PR looks good to go.

[justinmayer]

Hi Patrick. I am so sorry, but I merged #44 and #45 before realizing that your contribution had not been merged yet. If it is not too much to ask, would you be willing to rebase on current main and adjust the commits on this branch to incorporate the parts of your changes that are still relevant?

[do3cc]

No worries, I just did so.

[do3cc]

I have also changed the github workflow again. I got some feedback from earlier reviews not do the optimizations that I just reverted and I somehow managed to loose them during the refactoring.

[justinmayer]

Many thanks to @do3cc for the enhancements (and patience) as well as to @venthur and @hugovk for reviewing! 🥇