Can't generate pdf for cmu-user manual
Running
cd src/docs/cmu-user
make cmu-user-letter.pdf
fails with an error message from tex:
[177] [178] [179] [180] [181] [182] [183]) [184]
No file cmu-user-letter.fnd.
No file cmu-user-letter.vnd.
No file cmu-user-letter.tnd.
No file cmu-user-letter.cnd.
(./cmu-user-letter.aux
! Missing \endcsname inserted.
<to be read again>
\unhbox
l.1656 ...3.3}{180}{Strings}{subsection.13.3.3}{}}
git bisect says commit [ccd159f1] is the culprit.