Add SO_REUSEADDR option before binding to port

Author: elias-a

vpython/no_notebook.py

@@ -60,6 +60,7 @@ def signal_handler(signal, frame):
 
 def find_free_port(port):
     s = socket.socket()
+    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
     s.bind(('', port))
     return s.getsockname()[1]