I am using jupyterhub 1.1.4 and I realised just now that there is no error output when you develop a function for a callback. Just take a look at this piece of code:
from ipywidgets import widgets from IPython.display import display def testfun(args): i = 'a'.index('b') text = widgets.Button(description='Example Text') text.on_click(testfun) display(text)
It seems to work. Does it? No: There is an error. BUT YOU WILL NOT GET ANY INFORMATION THAT THEREW IS AN ERROR. There is no output at all!!
I think that needs to be fixed asap.