bpo-34084: Fix setting an error message for the "Barry as BDFL" easter egg. (GH-8262) (GH-8423)

(cherry picked from commit aba24ff3601ddc86b85e01880a8be596fb799287)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 9b9d63c..c4ec5ac 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -1348,6 +1348,10 @@
             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";