OSError caused by decode error should use string argument to be in li…

…ne with rest of module

Tests/test_file_libtiff.py

@@ -1146,7 +1146,7 @@ def test_realloc_overflow(self, monkeypatch: pytest.MonkeyPatch) -> None:
                 im.load()
 
             # Assert that the error code is IMAGING_CODEC_MEMORY
-            assert str(e.value) == "-9"
+            assert str(e.value) == "decoder error: -9"
 
     @pytest.mark.parametrize("compression", ("tiff_adobe_deflate", "jpeg"))
     def test_save_multistrip(self, compression: str, tmp_path: Path) -> None:

src/PIL/TiffImagePlugin.py

@@ -1406,7 +1406,8 @@ def _load_libtiff(self) -> Image.core.PixelAccess | None:
             self.fp = None  # might be shared
 
         if err < 0:
-            raise OSError(err)
+            msg = f"decoder error: {err}"
+            raise OSError(msg)
 
         return Image.Image.load(self)