Handle new SyntaxError tuple on 3.10

Closes #1372

tests/integration/test_checker.py

@@ -1,4 +1,5 @@
 """Integration tests for the checker submodule."""
+import sys
 from unittest import mock
 
 import pytest
@@ -336,3 +337,26 @@ def test_acquire_when_multiprocessing_pool_can_not_initialize():
 
     pool.assert_called_once_with(2, checker._pool_init)
     assert result is None
+
+
+def test_handling_syntaxerrors_across_pythons():
+    """Verify we properly handle exception argument tuples.
+
+    Python 3.10 added more information to the SyntaxError parse token tuple.
+    We need to handle that correctly to avoid crashing.
+    https://github.com/PyCQA/flake8/issues/1372
+    """
+    if sys.version_info < (3, 10):  # pragma: no cover (<3.10)
+        # Python 3.9 or older
+        err = SyntaxError(
+            "invalid syntax", ("<unknown>", 2, 5, "bad python:\n")
+        )
+        expected = (2, 4)
+    else:  # pragma: no cover (3.10+)
+        err = SyntaxError(
+            "invalid syntax", ("<unknown>", 2, 1, "bad python:\n", 2, 11)
+        )
+        expected = (2, 1)
+    file_checker = checker.FileChecker("-", {}, mock.MagicMock())
+    actual = file_checker._extract_syntax_information(err)
+    assert actual == expected