Fix pytests and enable parallel registry tests

test/testutil.py

@@ -0,0 +1,14 @@
+import socket
+
+def get_open_port():
+  """ Retrieves an open port on the system. """
+
+  # Bind a socket to a random port. We can then ask for the port number,
+  # and return it.
+  s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+  s.bind(("", 0))
+  s.listen(1)
+  port = s.getsockname()[1]
+  s.close()
+
+  return port