Issue #16504: Catch SyntaxErrors raised by tokenizer in IDLE.

Patch by Roger Serwy.

Lib/idlelib/EditorWindow.py

@@ -1618,7 +1618,7 @@ class IndentSearcher(object):
                 tokens = _tokenize.generate_tokens(self.readline)
                 for token in tokens:
                     self.tokeneater(*token)
-            except _tokenize.TokenError:
+            except (_tokenize.TokenError, SyntaxError):
                 # since we cut off the tokenizer early, we can trigger
                 # spurious errors
                 pass

Misc/NEWS

@@ -182,6 +182,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #16504: IDLE now catches SyntaxErrors raised by tokenizer. Patch by
+  Roger Serwy.
+
 - Issue #16618: Make glob.glob match consistently across strings and bytes
   regarding leading dots.  Patch by Serhiy Storchaka.