AttributeError: type object 'IOLoop' has no attribute 'initialized'

[bagjohn]

After navigating to the desired folder where we want to download the repository :
git clone https://github.com/projectmesa/mesa.git

Now navigating to a random example e.g. :
cd mesa/examples/Schelling

the example should run by typing :
python3 run.py

For some reason I get an unexpected error :
AttributeError: type object 'IOLoop' has no attribute 'initialized'

And it's true because :

1. in visualization/ModularVisualization.py in the class ModularServer in def launch() there is
   startLoop = not tornado.ioloop.IOLoop.initialized()
   2 but in tornado/ioloop.py in the class IOloop there is no attribute initialized!

Any help?

[bagjohn]

Fixed that at least temporarily by adding this to tornado/ioloop.py in class IOloop:

def initialized() :
        return False

[bagjohn]

A friend fixed it, it's a tornado version problem. Downgrade with this command: pip install tornado==4.5.3

Solution from here

[jackiekazil]

@bagjohn Ty for this! This is fixed in our next release. Hopefully no one will run into this problem again!