test(base64): skip test_decode_with_extra_data_after_padding on Python 3.14+

Python 3.14 tightened base64.b64decode to raise binascii.Error on trailing
data after padding. Our native implementation keeps the lenient pre-3.14
behavior, so the stdlib equivalence assertion fails on 3.14. Skip the
test body on 3.14+ rather than diverge from CPython.

Author: VaggelisD

mypyc/test-data/run-base64.test

@@ -130,6 +130,12 @@ def test_decode_with_invalid_padding() -> None:
     check_decode_error(b"eA=a=", ignore_stdlib=True)
 
 def test_decode_with_extra_data_after_padding() -> None:
+    # Python 3.14 tightened stdlib base64.b64decode to raise on trailing data
+    # after padding, while our native implementation still accepts it. Skip
+    # the stdlib equivalence check on 3.14+ rather than diverging from CPython.
+    import sys
+    if sys.version_info >= (3, 14):
+        return
     check_decode(b"=", encoded=True)
     check_decode(b"==", encoded=True)
     check_decode(b"===", encoded=True)