Export Notebook to PDF "Text line contains an invalid character"

[spestana]

Description:
On JupyterHub with a notebook containing a cell using ? to output the docstring help, Exporting Notebook to PDF raised an "500 : Internal Server Error" from and nbconvert error (see full error text below).

nbconvert version: 5.6.1

jupyter version:

$ jupyter --version
jupyter core     : 4.6.1
jupyter-notebook : 6.0.3
qtconsole        : not installed
ipython          : 7.11.1
ipykernel        : 5.1.4
jupyter client   : 5.3.4
jupyter lab      : 1.2.5
nbconvert        : 5.6.1
ipywidgets       : 7.5.1
nbformat         : 5.0.4
traitlets        : 4.3.3

Steps to reproduce:

• Download the attached notebook, open in JupyterHub, and run the two cells

• Go to File>Export Notebook As...>Export Notebook to PDF

• Receive error output

Full error text output:

nbconvert failed: PDF creating failed, captured latex output:
Failed to run "['xelatex', './notebook.tex', '-quiet']" command:
This is XeTeX, Version 3.14159265-2.6-0.99998 (TeX Live 2017/Debian) (preloaded format=xelatex)
 restricted \write18 enabled.
entering extended mode
(./notebook.tex
LaTeX2e <2017-04-15>
Babel <3.18> and hyphenation patterns for 3 language(s) loaded.
(/usr/share/texlive/texmf-dist/tex/latex/base/article.cls
Document Class: article 2014/09/29 v1.4h Standard LaTeX document class
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* (1in=72.27pt=25.4mm, 1cm=28.453pt)

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Package hyperref Warning: Rerun to get /PageLabels entry.

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LaTeX Warning: No \author given.

! Text line contains an invalid character.
l.389 ^^[
         [0;31mSignature:^^[[0m ^^[[0mstats^^[[0m^^[[0;34m.^^[[0m^^[[0mchi2^...

? 
! Emergency stop.
l.389 ^^[
         [0;31mSignature:^^[[0m ^^[[0mstats^^[[0m^^[[0;34m.^^[[0m^^[[0mchi2^...

No pages of output.
Transcript written on notebook.log.

invalid-character-error.ipynb.txt

[LuisBL]

same error here

[radifar]

Have the same problem, still no solution?

[michaelaye]

A question mark really shouldn't break the export, still happening today.