Raise ve on bad gt (#4180)

* Raise a ValueError when conversion to generalizedtime fails

* added test for badasn1time value error

* pep8 compliance

* Addressing code review

+ VE now raises with ```{!r}``` formatting
+ Test now checks that the bad string made it into the VE message

* using ValueError.match

1 files changed, 12 insertions, 0 deletions

diff --git a/tests/x509/test_x509.py b/tests/x509/test_x509.py
index 4a34d4a9..720db78e 100644
--- a/tests/x509/test_x509.py
+++ b/tests/x509/test_x509.py
@@ -3752,6 +3752,18 @@ class TestOtherCertificate(object):
         with pytest.raises(ValueError):
             cert.public_key()
 
+    def test_bad_time_in_validity(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "badasn1time.pem"
+            ),
+            x509.load_pem_x509_certificate,
+            backend,
+        )
+
+        with pytest.raises(ValueError, match='19020701025736Z'):
+            cert.not_valid_after
+
 
 class TestNameAttribute(object):
     EXPECTED_TYPES = [