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