The problem is that IDLE uses a TCP Port (a network port), 8833 as far as I know, to connect to the python server. This port is not available. This could have some reasons. Perhaps there is no network running. I assume that is not the case. The Port might already be in use. Perhaps IDEL is still running. Give it a try
ps -ef | grep idel
Or, you started Idle stopped it and started it at once. It lasts a while to release the network port. This may take up to a minute. The last reason I could imagine is that, the port is used by another program.
netstat -tlnp |grep python
If the command outputs a line or more. Then there is most likely an idle process still running. Perhpas started by the autorunner.
If you find port 8833 in a line of the output and the last command did no find a result then, another programm blocks port 8833. It it is a name process it's name is shown at the end of the line.