Python 3.9 shuffled the exception hierarchy, have to look for IOError…

…, OSError one of which is common parent of both hierarchies

The change should've been API compatible, so that's not the reason for failing PR

https://docs.python.org/3.9/library/socket.html#socket.error

tests/system_test.py

@@ -384,7 +384,11 @@ def __init__(self, name=None, listen_port=None, wait=True,
             self.args += self.cl_args
         super(Http2Server, self).__init__(self.args, name=name, expect=expect)
         if wait:
-            self.wait_ready()
+            try:
+                self.wait_ready()
+            except Exception:
+                self.teardown()
+                raise
 
     def wait_ready(self, **retry_kwargs):
         """