Mark pytz support as deprecated

.github/workflows/unit_tests.yml

@@ -64,7 +64,8 @@ jobs:
 
           # Test the rest
           export TEST_WITH_OPT_DEPS='true'
-          pip install .[all]
+          # need to manually install pytz here, because it's no longer in the optional reqs
+          pip install .[all] pytz
           # `-n auto --dist worksteal` uses pytest-xdist to run tests on multiple CPU
           # workers. Increasing number of workers has little effect on test duration, but it seems
           # to increase flakyness.

telegram/ext/_defaults.py

@@ -59,6 +59,11 @@ class Defaults:
             inputs appearing throughout PTB, i.e. if a timezone naive date(time) object is passed
             somewhere, it will be assumed to be in :paramref:`tzinfo`. Defaults to
             :attr:`datetime.timezone.utc` otherwise.
+
+            .. deprecated:: NEXT.VERSION
+                Support for ``pytz`` timezones is deprecated and will be removed in future
+                versions.
+
         block (:obj:`bool`, optional): Default setting for the :paramref:`BaseHandler.block`
             parameter
             of handlers and error handlers registered through :meth:`Application.add_handler` and
@@ -146,6 +151,19 @@ class Defaults:
         self._block: bool = block
         self._protect_content: Optional[bool] = protect_content
 
+        if "pytz" in str(self._tzinfo.__class__):
+            # TODO: When dropping support, make sure to update _utils.datetime accordingly
+            warn(
+                message=PTBDeprecationWarning(
+                    version="NEXT.VERSION",
+                    message=(
+                        "Support for pytz timezones is deprecated and will be removed in "
+                        "future versions."
+                    ),
+                ),
+                stacklevel=2,
+            )
+
         if disable_web_page_preview is not None and link_preview_options is not None:
             raise ValueError(
                 "`disable_web_page_preview` and `link_preview_options` are mutually exclusive."

tests/ext/test_defaults.py

@@ -25,6 +25,7 @@ import pytest
 from telegram import LinkPreviewOptions, User
 from telegram.ext import Defaults
 from telegram.warnings import PTBDeprecationWarning
+from tests.auxil.envvars import TEST_WITH_OPT_DEPS
 from tests.auxil.slots import mro_slots
 
 
@@ -39,6 +40,16 @@ class TestDefaults:
         defaults = Defaults()
         assert defaults.tzinfo is dtm.timezone.utc
 
+    @pytest.mark.skipif(not TEST_WITH_OPT_DEPS, reason="pytz not installed")
+    def test_pytz_deprecation(self, recwarn):
+        import pytz
+
+        with pytest.warns(PTBDeprecationWarning, match="pytz") as record:
+            Defaults(tzinfo=pytz.timezone("Europe/Berlin"))
+
+        assert record[0].category == PTBDeprecationWarning
+        assert record[0].filename == __file__, "wrong stacklevel!"
+
     def test_data_assignment(self):
         defaults = Defaults()