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

Lib/idlelib/EditorWindow.py

@@ -1611,7 +1611,7 @@ class IndentSearcher(object):
         try:
             try:
                 _tokenize.tokenize(self.readline, self.tokeneater)
-            except _tokenize.TokenError:
+            except (_tokenize.TokenError, SyntaxError):
                 # since we cut off the tokenizer early, we can trigger
                 # spurious errors
                 pass

Misc/NEWS

@@ -164,6 +164,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #16504: IDLE now catches SyntaxErrors raised by tokenizer. Patch by
+  Roger Serwy.
+
 - Issue #16702: test_urllib2_localnet tests now correctly ignores proxies for
   localhost tests.