tests: Fix Path exception matching for Python 3.12

On Python 3.12 the `pathlib.Path()` exception string has changed to
`argument should be a str or an os.PathLike object where __fspath__
returns a str, not 'bool'`. Matching the whole exception string was
never a great idea, but it seems like `PathLike` will always be in it
somewhere.

Fixes: #16

tests/test_receive.py

@@ -1026,11 +1026,9 @@ def test_load_unknown(self, tmp_path, caplog):
         assert expected_log_record in caplog.record_tuples
 
     def test_load_invalid(self, tmp_path):
-        with pytest.raises(receive.OTReceiveConfigError) as excinfo:
+        # Passing a non-path as the config file should fail.
+        with pytest.raises(receive.OTReceiveConfigError, match='PathLike'):
             receive.OTReceiveConfig.load([True])
-        assert str(excinfo.value) == (
-            'expected str, bytes or os.PathLike object, not bool'
-        )
 
         path = tmp_path / 'ostree-receive.conf'
         data = {