use kw-only args for install_find_links() fixture

tests/functional/test_install.py

@@ -10,6 +10,7 @@
 from typing import Callable, Dict, Iterable, List, Optional, Tuple
 
 import pytest
+from mypy_extensions import NamedArg
 
 from pip._internal.cli.status_codes import ERROR, SUCCESS
 from pip._internal.models.index import PyPI, TestPyPI
@@ -2372,13 +2373,19 @@ def test_install_logs_pip_version_in_debug(
     assert_re_match(pattern, result.stdout)
 
 
+_InstallFindLinks = Callable[
+    [Iterable[str], NamedArg(bool, "dry_run"), NamedArg(Optional[Path], "target_dir")],
+    TestPipResult,
+]
+
+
 @pytest.fixture
 def install_find_links(
     script: PipTestEnvironment,
     data: TestData,
-) -> Callable[[Iterable[str], bool, Optional[Path]], TestPipResult]:
+) -> _InstallFindLinks:
     def install(
-        args: Iterable[str], dry_run: bool, target_dir: Optional[Path]
+        args: Iterable[str], *, dry_run: bool, target_dir: Optional[Path]
     ) -> TestPipResult:
         return script.pip(
             "install",
@@ -2407,7 +2414,7 @@ def install(
 def test_install_dry_run_nothing_installed(
     script: PipTestEnvironment,
     tmpdir: Path,
-    install_find_links: Callable[[Iterable[str], bool, Optional[Path]], TestPipResult],
+    install_find_links: _InstallFindLinks,
     with_target_dir: bool,
 ) -> None:
     """Test that pip install --dry-run logs what it would install, but doesn't actually
@@ -2418,7 +2425,7 @@ def test_install_dry_run_nothing_installed(
     else:
         install_dir = None
 
-    result = install_find_links(["simple"], True, install_dir)
+    result = install_find_links(["simple"], dry_run=True, target_dir=install_dir)
     assert "Would install simple-3.0" in result.stdout
     assert "Successfully installed" not in result.stdout
 
@@ -2428,7 +2435,7 @@ def test_install_dry_run_nothing_installed(
 
     # Ensure that the same install command would normally have worked if not for
     # --dry-run.
-    install_find_links(["simple"], False, install_dir)
+    install_find_links(["simple"], dry_run=False, target_dir=install_dir)
     if with_target_dir:
         assert os.listdir(install_dir)
     else: