Widgets with 100% width produce erroneous horizontal scroll bar

[dokempf]

We are fitting widgets into layout containers a lot by specifying width='100%' to make them fit exactly. However, many of these still produce a horizontal scrollbar. I consider this a bug of ipywidgets which should be researched and potentially reported upstream.

[dokempf]

The min_width field of ipywidgets.Layout can be set to a smaller number to prevent this. It might be necessary in many places though to completely prevent scrollbars.

[dokempf]

Another observation: Often wrapping ipwidgets.VBox creates the problem in the first place.