make pdfdocs problem with 4.13-rc4

[Jim Davis]

On my Fedora 26 workstation, with the latest patches, running make
pdfdocs stops with

[jim@krebstar ~]$ tail /tmp/make-pdfdocs.out

Underfull \hbox (badness 10000) in paragraph at lines 3980--3983
[]\EU1/DejaVuSans(0)/m/n/10 Threshold below
[31]
! Missing \endgroup inserted.
<inserted text>
                \endgroup
l.4114 \begin{savenotes}\sphinxattablestart

?

Pressing the return key (many times) doesn't solve the problem, and
eventually make fizzles out with

make[2]: *** [Makefile:33: media.pdf] Error 1
make[1]: *** [Documentation/Makefile:83: pdfdocs] Error 2
make: *** [Makefile:1473: pdfdocs] Error 2

Oh, and

[jim@krebstar ~]$ grep 'LaTeX Warning:' /tmp/make-pdfdocs.out | wc -l
5438

-- 
Jim