Unsupport leap seconds.

It's unclear to me yet what to do here.

Upstream we seem to read that these should be valid, but in particular,
strict-rfc3339 doesn't support them because they'd require up to date
tzdata.

Author: Julian

jsonschema/tests/test_jsonschema_test_suite.py

@@ -114,6 +114,17 @@ def missing_date_fromisoformat(test):
     ),
 )
 
+def leap_second(test):
+    return skip(
+        message="Leap seconds are unsupported.",
+        subject="time",
+        description="a valid time string with leap second",
+    )(test) or skip(
+        message="Leap seconds are unsupported.",
+        subject="time",
+        description="a valid time string with leap second with offset",
+    )(test)
+
 
 TestDraft3 = DRAFT3.to_unittest_testcase(
     DRAFT3.tests(),
@@ -369,6 +380,7 @@ def missing_date_fromisoformat(test):
         narrow_unicode_build(test)
         or missing_date_fromisoformat(test)
         or allowed_leading_zeros(test)
+        or leap_second(test)
         or missing_format(draft7_format_checker)(test)
         or complex_email_validation(test)
         or skip(