Remove --py2 argument (#15670)

mypy/defaults.py

@@ -3,8 +3,6 @@
 import os
 from typing import Final
 
-PYTHON2_VERSION: Final = (2, 7)
-
 # Earliest fully supported Python 3.x version. Used as the default Python
 # version in tests. Mypy wheels should be built starting with this version,
 # and CI tests should be run on this version (and later versions).

mypy/main.py

@@ -594,14 +594,6 @@ def add_invertible_flag(
         help="Type check code assuming it will be running on Python x.y",
         dest="special-opts:python_version",
     )
-    platform_group.add_argument(
-        "-2",
-        "--py2",
-        dest="special-opts:python_version",
-        action="store_const",
-        const=defaults.PYTHON2_VERSION,
-        help="Use Python 2 mode (same as --python-version 2.7)",
-    )
     platform_group.add_argument(
         "--platform",
         action="store",

mypy/test/helpers.py

@@ -345,7 +345,7 @@ def parse_options(
         options.force_union_syntax = True
 
     # Allow custom python version to override testfile_pyversion.
-    if all(flag.split("=")[0] not in ["--python-version", "-2", "--py2"] for flag in flag_list):
+    if all(flag.split("=")[0] != "--python-version" for flag in flag_list):
         options.python_version = testfile_pyversion(testcase.file)
 
     if testcase.config.getoption("--mypy-verbose"):