bibtexparser fails mysteriously

[kmccurley]

I observed the following in cc1-3-106:

Unable to parse region of bibtex: @article{deBruijn, author = {de Bruijn, N. G.}, journal = {Indag. Math.}, note = {Nederl. Akad. Wetensch. Proc. Ser. A {\bf 69}}, pages = {239--247}, title = {On the number of positive integers {
} and free prime factors {
}. {II}}, volume = {28}, year = {1966}, }

This arises from bibtexmarkup.py when bibtexparser encounters a block that it cannot parse. I am unable to reproduce this problem using the version of bibtexparser in the venv for the docker instance, so I am at a loss as to what is causing the problem. The paper has other compilation problems so it's possible that this will disappear.