pi@raspberrypi ~/yubi/yubico-c $ make check
Making check in .
make[1]: Entering directory '/home/pi/yubi/yubico-c'
/bin/bash /home/pi/yubi/yubico-c/build-aux/missing a2x --format=manpage -a revdate="Version 1.14" modhex.1.txt
a2x: ERROR: "xmllint" --nonet --noout --valid "/home/pi/yubi/yubico-c/modhex.1.xml" returned non-zero exit status 127
Makefile:1148: recipe for target 'modhex.1' failed
make[1]: *** [modhex.1] Error 1
make[1]: Leaving directory '/home/pi/yubi/yubico-c'
Makefile:719: recipe for target 'check-recursive' failed
make: *** [check-recursive] Error 1