Fix mypy 1.14.1 error

Author: notatallshaw

.pre-commit-config.yaml

@@ -28,7 +28,7 @@ repos:
       args: [--fix, --exit-non-zero-on-fix]
 
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: v1.13.0
+  rev: v1.14.1
   hooks:
   - id: mypy
     exclude: tests/data

src/pip/_internal/utils/unpacking.py

@@ -8,7 +8,7 @@
 import sys
 import tarfile
 import zipfile
-from typing import Iterable, List, Optional
+from typing import Iterable, List, Literal, Optional
 from zipfile import ZipInfo
 
 from pip._internal.exceptions import InstallationError
@@ -22,7 +22,7 @@
 
 logger = logging.getLogger(__name__)
 
-
+OPEN_MODE_TYPE = Literal['r', 'r:*', 'r:', 'r:gz', 'r:bz2', 'r:xz']
 SUPPORTED_EXTENSIONS = ZIP_EXTENSIONS + TAR_EXTENSIONS
 
 try:
@@ -162,7 +162,7 @@ def untar_file(filename: str, location: str) -> None:
     """
     ensure_dir(location)
     if filename.lower().endswith(".gz") or filename.lower().endswith(".tgz"):
-        mode = "r:gz"
+        mode: OPEN_MODE_TYPE = "r:gz"
     elif filename.lower().endswith(BZ2_EXTENSIONS):
         mode = "r:bz2"
     elif filename.lower().endswith(XZ_EXTENSIONS):