DOC: limit error traceback to one line for expected exceptions

[jorisvandenbossche]

xref #10674 (comment)

When using :okexcept:, limit the traceback to one line (or as a separate option + try to push to ipython upstream afterwards)

[jorisvandenbossche]

Basically, I think just need to add something like:

 if is_okexcept and "Traceback" in output:
    output = truncated(output)

here: https://github.com/pydata/pandas/blob/master/doc/sphinxext/ipython_sphinxext/ipython_directive.py#L482

[terrytangyuan]

Hi Joris @jorisvandenbossche, how would this output get truncated? So output is a list. Do you want only the first element (output[0]) or?

[jorisvandenbossche]

@terrytangyuan sorry, I apparantly didn't link to this issue properly, but there is already a PR for this: #10727 is merged, but also reverted because it failed for some reason on travis. And a second try here: #10925.
For some reason, this still does not work on travis (locally it all works for me). So if you want to try that out locally, always welcome!