Issue #13153: Tkinter functions now raise TclError instead of ValueError when

a unicode argument contains non-BMP character.

Misc/NEWS

@@ -205,6 +205,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #13153: Tkinter functions now raise TclError instead of ValueError when
+  a unicode argument contains non-BMP character.
+
 - Issue #9669: Protect re against infinite loops on zero-width matching in
   non-greedy repeat.  Patch by Matthew Barnett.
 

Modules/_tkinter.c

@@ -987,8 +987,10 @@ AsObj(PyObject *value)
         for (i = 0; i < size; i++) {
             if (inbuf[i] >= 0x10000) {
                 /* Tcl doesn't do UTF-16, yet. */
-                PyErr_SetString(PyExc_ValueError,
-                                "unsupported character");
+                PyErr_Format(Tkinter_TclError,
+                             "character U+%x is above the range "
+                             "(U+0000-U+FFFF) allowed by Tcl",
+                             (int)inbuf[i]);
                 ckfree(FREECAST outbuf);
                 return NULL;
             }