Fix undefined manager

[jtpio]

WidgetManager takes a manager as a second argument which was not defined in this case, resulting in a: ReferenceError: manager is not defined

Tested with:

from ipywidgets import IntSlider, Label, Output

out = Output()
slider = IntSlider(min=0, max=100)
label = Label(value='Test')

@out.capture()
def on_change(change):
    display(label)

slider.observe(on_change, names='value')

with out:
    display(slider)    
out

Although this change seems to fix the manager is not defined error, the code posted above still doesn't work as expected (need more investigation).

[SylvainCorlay]

Sorry this fell between the cracks. Will investigate this week.

[SylvainCorlay]

(rebased)

[SylvainCorlay]

The issue with displaying widgets in an output widget appears to be unrelated to this (but related to the issue people experienced with ipympl at the workshop).

Will be merging this and iterate on the output widget.

[jtpio]

Sounds good, seems to be a different issue indeed.