config: let main() accept any os.PathLike instead of just py.path.local

Really it ought to only take the List[str], but for backward
compatibility, at least get rid of the explicit py.path.local check.

src/_pytest/config/__init__.py

@@ -128,7 +128,7 @@ def filter_traceback_for_conftest_import_failure(
 
 
 def main(
-    args: Optional[Union[List[str], py.path.local]] = None,
+    args: Optional[Union[List[str], "os.PathLike[str]"]] = None,
     plugins: Optional[Sequence[Union[str, _PluggyPlugin]]] = None,
 ) -> Union[int, ExitCode]:
     """Perform an in-process test run.
@@ -295,13 +295,15 @@ def get_plugin_manager() -> "PytestPluginManager":
 
 
 def _prepareconfig(
-    args: Optional[Union[py.path.local, List[str]]] = None,
+    args: Optional[Union[List[str], "os.PathLike[str]"]] = None,
     plugins: Optional[Sequence[Union[str, _PluggyPlugin]]] = None,
 ) -> "Config":
     if args is None:
         args = sys.argv[1:]
-    elif isinstance(args, py.path.local):
-        args = [str(args)]
+    # TODO: Remove type-ignore after next mypy release.
+    # https://github.com/python/typeshed/commit/076983eec45e739c68551cb6119fd7d85fd4afa9
+    elif isinstance(args, os.PathLike):  # type: ignore[misc]
+        args = [os.fspath(args)]
     elif not isinstance(args, list):
         msg = "`args` parameter expected to be a list of strings, got: {!r} (type: {})"
         raise TypeError(msg.format(args, type(args)))

testing/test_collection.py

@@ -277,7 +277,7 @@ class TestCollectPluginHookRelay:
                     wascalled.append(path)
 
         pytester.makefile(".abc", "xyz")
-        pytest.main(py.path.local(pytester.path), plugins=[Plugin()])
+        pytest.main(pytester.path, plugins=[Plugin()])
         assert len(wascalled) == 1
         assert wascalled[0].ext == ".abc"