bpo-41520: Fix second codeop regression (GH-21848)

* bpo-41520: Fix second codeop repression

Fix the repression introduced by the initial regression fix.

Lib/codeop.py

@@ -85,9 +85,9 @@ def _maybe_compile(compiler, source, filename, symbol):
         pass
 
     # Catch syntax warnings after the first compile
-    # to emit SyntaxWarning at most once.
+    # to emit warnings (SyntaxWarning, DeprecationWarning) at most once.
     with warnings.catch_warnings():
-        warnings.simplefilter("error", SyntaxWarning)
+        warnings.simplefilter("error")
 
         try:
             code1 = compiler(source + "\n", filename, symbol)

Lib/test/test_codeop.py

@@ -307,14 +307,17 @@ class CodeopTests(unittest.TestCase):
 
     def test_warning(self):
         # Test that the warning is only returned once.
-        with warnings_helper.check_warnings((".*literal", SyntaxWarning)) as w:
-            compile_command("0 is 0")
-            self.assertEqual(len(w.warnings), 1)
+        with warnings_helper.check_warnings(
+                (".*literal", SyntaxWarning),
+                (".*invalid", DeprecationWarning),
+                ) as w:
+            compile_command(r"'\e' is 0")
+            self.assertEqual(len(w.warnings), 2)
 
         # bpo-41520: check SyntaxWarning treated as an SyntaxError
-        with self.assertRaises(SyntaxError):
+        with warnings.catch_warnings(), self.assertRaises(SyntaxError):
             warnings.simplefilter('error', SyntaxWarning)
-            compile_command('1 is 1\n', symbol='exec')
+            compile_command('1 is 1', symbol='exec')
 
 
 if __name__ == "__main__":

Misc/NEWS.d/next/Library/2020-08-12-13-25-16.bpo-41520.BEUWa4.rst

@@ -1 +1 @@
-Fix :mod:`codeop` regression: it no longer ignores :exc:`SyntaxWarning`.
+Fix :mod:`codeop` regression that prevented turning compile warnings into errors.