Remove 3.9 support from CI and tests (#15401)

tests/mypy_test.py

@@ -44,7 +44,7 @@ except ImportError:
     print_error("Cannot import mypy. Did you install it?")
     sys.exit(1)
 
-SUPPORTED_VERSIONS = ["3.14", "3.13", "3.12", "3.11", "3.10", "3.9"]
+SUPPORTED_VERSIONS = ["3.14", "3.13", "3.12", "3.11", "3.10"]
 SUPPORTED_PLATFORMS = ("linux", "win32", "darwin")
 DIRECTORIES_TO_TEST = [STDLIB_PATH, STUBS_PATH]
 

tests/regr_test.py

@@ -41,7 +41,7 @@ VENV_DIR = ".venv"
 TYPESHED = "typeshed"
 
 SUPPORTED_PLATFORMS = ["linux", "darwin", "win32"]
-SUPPORTED_VERSIONS = ["3.14", "3.13", "3.12", "3.11", "3.10", "3.9"]
+SUPPORTED_VERSIONS = ["3.14", "3.13", "3.12", "3.11", "3.10"]
 
 
 def distribution_with_test_cases(distribution_name: str) -> DistributionTests:

tests/runtests.py

@@ -50,7 +50,7 @@ def main() -> None:
     parser.add_argument(
         "--python-version",
         default=None,
-        choices=("3.9", "3.10", "3.11", "3.12", "3.13", "3.14"),
+        choices=("3.10", "3.11", "3.12", "3.13", "3.14"),
         # We're using the oldest fully supported version because it's the most likely to produce errors
         # due to unsupported syntax, feature, or bug in a tool.
         help="Target Python version for the test (defaults to oldest supported Python version).",

tests/typecheck_typeshed.py

@@ -14,7 +14,7 @@ from ts_utils.utils import colored, print_error
 ReturnCode: TypeAlias = int
 
 SUPPORTED_PLATFORMS = ("linux", "darwin", "win32")
-SUPPORTED_VERSIONS = ("3.14", "3.13", "3.12", "3.11", "3.10", "3.9")
+SUPPORTED_VERSIONS = ("3.14", "3.13", "3.12", "3.11", "3.10")
 LOWEST_SUPPORTED_VERSION = min(SUPPORTED_VERSIONS, key=lambda x: int(x.split(".")[1]))
 DIRECTORIES_TO_TEST = ("scripts", "tests")
 EMPTY: list[str] = []