Add PIL._imaging.NotSupportedError

Author: akx

src/_imaging.c

@@ -382,6 +382,19 @@ ImagingError_ModeError(void) {
     return NULL;
 }
 
+// Derives from both NotImplementedError and ValueError
+// (as the functions above raise ValueErrors).
+static PyObject *ImagingNotSupportedError = NULL;
+
+void *
+ImagingError_NotSupportedError(const char *message) {
+    PyErr_SetString(
+        ImagingNotSupportedError ? ImagingNotSupportedError : PyExc_NotImplementedError,
+        (message) ? (char *)message : "operation not supported"
+    );
+    return NULL;
+}
+
 void *
 ImagingError_ValueError(const char *message) {
     PyErr_SetString(
@@ -4326,6 +4339,24 @@ setup_module(PyObject *m) {
         return -1;
     }
 
+    if (ImagingNotSupportedError == NULL) {
+        // NotSupportedError derives from both NotImplementedError and ValueError,
+        // for compatibility with `except ValueError`.
+        PyObject *bases = PyTuple_Pack(2, PyExc_NotImplementedError, PyExc_ValueError);
+        if (bases == NULL) {
+            return -1;
+        }
+        ImagingNotSupportedError =
+            PyErr_NewException("PIL._imaging.NotSupportedError", bases, NULL);
+        Py_DECREF(bases);
+        if (ImagingNotSupportedError == NULL) {
+            return -1;
+        }
+    }
+    if (PyModule_AddObjectRef(m, "NotSupportedError", ImagingNotSupportedError) < 0) {
+        return -1;
+    }
+
 #ifdef HAVE_LIBJPEG
     {
         extern const char *ImagingJpegVersion(void);

src/libImaging/Imaging.h

@@ -273,6 +273,10 @@ extern void *
 ImagingError_Mismatch(void); /* maps to ValueError by default */
 extern void *
 ImagingError_ValueError(const char *message);
+extern void *
+ImagingError_NotSupportedError(
+    const char *message
+); /* derives from NotImplementedError and ValueError */
 
 /* Transform callbacks */
 /* ------------------- */