Fix #106372: Wrong message in driver for disabled execution

When using a python expression, its execution is disabled by
default unless specified differently in the user preferences.
Previously this only produced the error
"Error: Invalid Python expression". However that isn't really the correct error.

Now the error reads "Python restricted for security".

I've added a new flag to the driver `DRIVER_FLAG_PYTHON_BLOCKED` that is set
if the driver can't run because python is blocked

Co-authored by Phillip Oeser

Pull Request: https://projects.blender.org/blender/blender/pulls/124587

source/blender/editors/space_graph/graph_buttons.cc

@@ -1033,17 +1033,16 @@ static void graph_draw_driver_settings_panel(uiLayout *layout,
     col = uiLayoutColumn(layout, true);
     block = uiLayoutGetBlock(col);
 
-    if (driver->flag & DRIVER_FLAG_INVALID) {
+    if (driver->flag & DRIVER_FLAG_PYTHON_BLOCKED) {
+      /* TODO: Add button to enable? */
+      uiItemL(col, RPT_("Python restricted for security"), ICON_ERROR);
+      uiItemL(col, RPT_("Slow Python expression"), ICON_INFO);
+    }
+    else if (driver->flag & DRIVER_FLAG_INVALID) {
       uiItemL(col, RPT_("ERROR: Invalid Python expression"), ICON_CANCEL);
     }
     else if (!BKE_driver_has_simple_expression(driver)) {
-      if ((G.f & G_FLAG_SCRIPT_AUTOEXEC) == 0) {
-        /* TODO: Add button to enable? */
-        uiItemL(col, RPT_("Python restricted for security"), ICON_ERROR);
-      }
-      else {
-        uiItemL(col, RPT_("Slow Python expression"), ICON_INFO);
-      }
+      uiItemL(col, RPT_("Slow Python expression"), ICON_INFO);
     }
 
     /* Explicit bpy-references are evil. Warn about these to prevent errors */

source/blender/makesdna/DNA_anim_types.h

@@ -561,7 +561,8 @@ typedef enum eDriver_Flags {
   DRIVER_FLAG_RECOMPILE = (1 << 3),
   /** The names are cached so they don't need have python unicode versions created each time */
   DRIVER_FLAG_RENAMEVAR = (1 << 4),
-  // DRIVER_FLAG_UNUSED_5 = (1 << 5),
+  /* Set if the driver cannot run because it uses Python which isn't allowed to execute. */
+  DRIVER_FLAG_PYTHON_BLOCKED = (1 << 5),
   /** Include 'self' in the drivers namespace. */
   DRIVER_FLAG_USE_SELF = (1 << 6),
 } eDriver_Flags;

source/blender/python/intern/bpy_driver.cc

@@ -689,6 +689,7 @@ float BPY_driver_exec(PathResolvedRNA *anim_rna,
         Py_DECREF(expr_code);
         expr_code = nullptr;
         PyTuple_SET_ITEM(((PyObject *)driver_orig->expr_comp), 0, nullptr);
+        driver_orig->flag |= DRIVER_FLAG_PYTHON_BLOCKED;
       }
     }
   }