Convert X509ExtTests to use pytest-style tests (#564)

diff --git a/src/OpenSSL/crypto.py b/src/OpenSSL/crypto.py
index 52fcdaf..e1558ed 100644
--- a/src/OpenSSL/crypto.py
+++ b/src/OpenSSL/crypto.py
@@ -316,6 +316,8 @@
         :return: The number of bits of the key.
         """
         return _lib.EVP_PKEY_bits(self._pkey)
+
+
 PKeyType = PKey
 
 
@@ -2180,6 +2182,7 @@
         string_type = _lib.OBJ_nid2sn(nid)
         return _ffi.string(string_type)
 
+
 PKCS7Type = PKCS7