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

diff --git a/src/OpenSSL/SSL.py b/src/OpenSSL/SSL.py
index 7ebf7e0..f92c064 100644
--- a/src/OpenSSL/SSL.py
+++ b/src/OpenSSL/SSL.py
@@ -1065,6 +1065,7 @@
         _lib.SSL_CTX_set_alpn_select_cb(
             self._context, self._alpn_select_callback, _ffi.NULL)
 
+
 ContextType = Context
 
 
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
 
 
diff --git a/src/OpenSSL/rand.py b/src/OpenSSL/rand.py
index a22f9e5..8f51ad8 100644
--- a/src/OpenSSL/rand.py
+++ b/src/OpenSSL/rand.py
@@ -31,6 +31,7 @@
     See :manpage:`err(3)` for more information.
     """
 
+
 _raise_current_error = partial(_exception_from_error_queue, Error)
 
 _unspecified = object()
@@ -202,6 +203,7 @@
     """
     _lib.RAND_screen()
 
+
 if getattr(_lib, 'RAND_screen', None) is None:
     del screen