bpo-40661: Fix segfault when parsing invalid input

Lib/test/test_peg_parser.py

@@ -591,6 +591,7 @@ def f(*a, b):
     ("f-string_single_closing_brace", "f'}'"),
     ("from_import_invalid", "from import import a"),
     ("from_import_trailing_comma", "from a import b,"),
+    ("import_non_ascii_syntax_error", "import ä £"),
     # This test case checks error paths involving tokens with uninitialized
     # values of col_offset and end_col_offset.
     ("invalid indentation",

Lib/test/test_syntax.py

@@ -659,6 +659,9 @@
     Traceback (most recent call last):
     SyntaxError: cannot assign to __debug__
 
+    >>> import ä £
+    Traceback (most recent call last):
+    SyntaxError: invalid character '£' (U+00A3)
 """
 
 import re