bpo-34084: Fix setting an error message for the "Barry as BDFL" easter egg. (GH-8262)

Python/pythonrun.c

@@ -1348,6 +1348,10 @@ err_input(perrdetail *err)
             msg = "unexpected indent";
         else if (err->token == DEDENT)
             msg = "unexpected unindent";
+        else if (err->expected == NOTEQUAL) {
+            errtype = PyExc_SyntaxError;
+            msg = "with Barry as BDFL, use '<>' instead of '!='";
+        }
         else {
             errtype = PyExc_SyntaxError;
             msg = "invalid syntax";