Update invalid EC key test for compatibility with upcoming OpenSSL ch…

…anges (pyca#7833)

One of the tests checking behavior with invalid EC keys hardcoded the
error reason.

This commit replaces the string matching with a regex to match both the
current string and a new reason, introduced by upcoming OpenSSL
changes [0], which would otherwise trigger a false positive failure.

[0]: openssl/openssl#19681

tests/hazmat/primitives/test_ec.py

@@ -479,7 +479,9 @@ def test_load_invalid_ec_key_from_pem(self, backend):
         # BoringSSL rejects infinity points before it ever gets to us, so it
         # uses a more generic error message.
         match = (
-            "infinity" if not backend._lib.CRYPTOGRAPHY_IS_BORINGSSL else None
+            r"infinity|invalid form"
+            if not backend._lib.CRYPTOGRAPHY_IS_BORINGSSL
+            else None
         )
         with pytest.raises(ValueError, match=match):
             serialization.load_pem_public_key(