chore(gapic): clean up Python version guards and imports in templates

Author: chalmerlowe

packages/gapic-generator/gapic/ads-templates/%namespace/%name/%version/__init__.py.j2

@@ -11,8 +11,8 @@ from {{package_path}} import gapic_version as package_version
 __version__ = package_version.__version__
 
 
-if sys.version_info < (3, 8):
-    raise ImportError('This module requires Python 3.8 or later.')
+if sys.version_info < (3, 10):
+    raise ImportError('This module requires Python 3.10 or later.')
 
 
 _lazy_type_to_package_map = {

packages/gapic-generator/gapic/ads-templates/%namespace/%name/__init__.py.j2

@@ -6,8 +6,8 @@ import importlib
 import sys
 
 
-if sys.version_info < (3, 8):
-    raise ImportError('This module requires Python 3.8 or later.')
+if sys.version_info < (3, 10):
+    raise ImportError('This module requires Python 3.10 or later.')
 
 
 _lazy_type_to_package_map = {

packages/gapic-generator/gapic/templates/%namespace/%name_%version/%sub/__init__.py.j2

@@ -10,12 +10,7 @@ import sys
 
 __version__ = package_version.__version__
 
-if sys.version_info >= (3, 8):  # pragma: NO COVER
-    from importlib import metadata
-else:  # pragma: NO COVER
-    # TODO(https://github.com/googleapis/python-api-core/issues/835): Remove
-    # this code path once we drop support for Python 3.7
-    import importlib_metadata as metadata
+from importlib import metadata
 
 {#  Import subpackages. -#}
 {% for subpackage, _ in api.subpackages|dictsort %}
@@ -65,20 +60,12 @@ else:   # pragma: NO COVER
 
         _py_version_str = sys.version.split()[0]
         _package_label = "{{package_path}}"
-        if sys.version_info < (3, 9):
+        if sys.version_info < (3, 10):
             warnings.warn("You are using a non-supported Python version " +
                           f"({_py_version_str}).  Google will not post any further " +
                           f"updates to {_package_label} supporting this Python version. " +
                           "Please upgrade to the latest Python version, or at " +
-                          f"least to Python 3.9, and then update {_package_label}.",
-                          FutureWarning)
-        if sys.version_info[:2] == (3, 9):
-            warnings.warn(f"You are using a Python version ({_py_version_str}) " +
-                          f"which Google will stop supporting in {_package_label} in " +
-                          "January 2026. Please " +
-                          "upgrade to the latest Python version, or at " +
-                          "least to Python 3.10, before then, and " +
-                          f"then update {_package_label}.",
+                          f"least to Python 3.10, and then update {_package_label}.",
                           FutureWarning)
 
         def parse_version_to_tuple(version_string: str):

packages/gapic-generator/gapic/templates/tests/unit/gapic/%name_%version/%sub/test_%service.py.j2

@@ -10,12 +10,8 @@ import os
 {% if api.all_method_settings.values()|map(attribute="auto_populated_fields", default=[])|list %}
 import re
 {% endif %}
-# try/except added for compatibility with python < 3.8
-try:
-    from unittest import mock
-    from unittest.mock import AsyncMock  # pragma: NO COVER
-except ImportError:  # pragma: NO COVER
-    import mock
+from unittest import mock
+from unittest.mock import AsyncMock
 
 import grpc
 from grpc.experimental import aio