allow the use of --show-traceback and --pdb with stubtest (#18037)

Mypy's error handling suggests using -`-show-traceback` and `--pdb` for
more information, and this can occur while running stubtest. This MR
adds support for both flags to stubtest so that the suggestions can be
followed without needing to figure out the equivalent mypy invocation
first.

Author: tungol

mypy/stubtest.py

@@ -1893,6 +1893,8 @@ class _Arguments:
     custom_typeshed_dir: str | None
     check_typeshed: bool
     version: str
+    show_traceback: bool
+    pdb: bool
 
 
 # typeshed added a stub for __main__, but that causes stubtest to check itself
@@ -1938,6 +1940,8 @@ def test_stubs(args: _Arguments, use_builtins_fixtures: bool = False) -> int:
         options.abs_custom_typeshed_dir = os.path.abspath(options.custom_typeshed_dir)
     options.config_file = args.mypy_config_file
     options.use_builtins_fixtures = use_builtins_fixtures
+    options.show_traceback = args.show_traceback
+    options.pdb = args.pdb
 
     if options.config_file:
 
@@ -2091,6 +2095,10 @@ def parse_options(args: list[str]) -> _Arguments:
     parser.add_argument(
         "--version", action="version", version="%(prog)s " + mypy.version.__version__
     )
+    parser.add_argument("--pdb", action="store_true", help="Invoke pdb on fatal error")
+    parser.add_argument(
+        "--show-traceback", "--tb", action="store_true", help="Show traceback on fatal error"
+    )
 
     return parser.parse_args(args, namespace=_Arguments())