i am new in ros and gazebo. i tried the to run the gymconstruct package in my local computer. when i launch the starttraining launch file it gives me an error:

[ERROR] [1545893390.519507, 10167.199000]: Current /odom not ready yet, retrying for getting odom.

when i check the topic info of odom, it says publisher: none and subscriber: * /turtlebot2_maze (http://mudassir:46109/)

I need help.