[3.9] bpo-42214: Fix check for NOTEQUAL token in the PEG parser for the barry_as_flufl rule (GH-23048) (GH-23051)

(cherry picked from commit 06f8c3328d)

Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>

Lib/test/test_syntax.py

@@ -947,6 +947,23 @@ pass
             self.fail("Empty line after a line continuation character is valid.")
 
 
+    def test_barry_as_flufl_with_syntax_errors(self):
+        # The "barry_as_flufl" rule can produce some "bugs-at-a-distance" if
+        # is reading the wrong token in the presence of syntax errors later
+        # in the file. See bpo-42214 for more information.
+        code = """
+def func1():
+    if a != b:
+        raise ValueError
+
+def func2():
+    try
+        return 1
+    finally:
+        pass
+"""
+        self._check_error(code, "invalid syntax")
+
 def test_main():
     support.run_unittest(SyntaxTestCase)
     from test import test_syntax