Warn when using Beam with Python 3.8 (#32484)

* Warn when using Beam with Python 3.8

* Call out in CHANGES.md

* formatting

CHANGES.md

@@ -82,6 +82,8 @@
 ## Deprecations
 
 * X behavior is deprecated and will be removed in X versions ([#X](https://github.com/apache/beam/issues/X)).
+* Python 3.8 is reaching EOL and support is being removed in Beam 2.61.0. The 2.60.0 release will warn users
+when running on 3.8. ([#31192](https://github.com/apache/beam/issues/31192))
 
 ## Bugfixes
 

sdks/python/apache_beam/__init__.py

@@ -75,6 +75,12 @@
         'This version of Apache Beam has not been sufficiently tested on '
         'Python %s.%s. You may encounter bugs or missing features.' %
         (sys.version_info.major, sys.version_info.minor))
+  elif sys.version_info.minor == 8:
+    warnings.warn(
+        'Python 3.8 reaches EOL in October 2024 and support will '
+        'be removed from Apache Beam in version 2.61.0. See '
+        'https://github.com/apache/beam/issues/31192 for more '
+        'information.')
   pass
 else:
   raise RuntimeError(

sdks/python/setup.py

@@ -278,6 +278,11 @@ def get_portability_package_data():
       'This version of Apache Beam has not been sufficiently tested on '
       'Python %s.%s. You may encounter bugs or missing features.' %
       (sys.version_info.major, sys.version_info.minor))
+elif sys.version_info.major == 3 and sys.version_info.minor == 8:
+  warnings.warn('Python 3.8 reaches EOL in October 2024 and support will '
+                'be removed from Apache Beam in version 2.61.0. See '
+                'https://github.com/apache/beam/issues/31192 for more '
+                'information.')
 
 if __name__ == '__main__':
   # In order to find the tree of proto packages, the directory