$ sudo make install
make  install-recursive
make[1]: Entering directory '/home/nathaniel/libostree-2018.6'
Making install in .
make[2]: Entering directory '/home/nathaniel/libostree-2018.6'
  GEN      man/ostree.1
I/O error : Attempt to load network entity http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl
warning: failed to load external entity "http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl"
cannot parse http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl
make[2]: *** [Makefile:9183: man/ostree.1] Error 4
make[2]: Leaving directory '/home/nathaniel/libostree-2018.6'
make[1]: *** [Makefile:7228: install-recursive] Error 1
make[1]: Leaving directory '/home/nathaniel/libostree-2018.6'
make: *** [Makefile:8464: install] Error 2