Cells with HTML output print the entire unformatted traceback instead of just the error message

[joelostblom]

When the output of a cell is regular text, any errors that are raised have their traceback truncated, which I find helpful. For example, this code:

import altair as alt
from vega_datasets import data

cars = data.cars()
alt.Chart(cars).mark_point().encode(
    x='Horsepower',
    y='Miles_per_Gallons',
).to_dict()

Prints only the error message, which makes it easy to see what went wrong:

However, when the output is HTML, such as when removing the to_dict() call above, the entire traceback is outputted and the ascii color codes are not respected which makes it very hard to read what is going on: