What to do when docbook generation complains about needing I/O during builds

[nh2]

For posterity, if you see during a sandboxed nix-build:

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"

then you need to add to your compile-time dependencies (nativeBuildInputs):

docbook5
docbook_xsl
docbook_xsl_ns

If you further get something like:

I/O error : Attempt to load network entity http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd
../man/sd_bus_message_append_basic.xml:3: warning: failed to load external entity "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

then you have to further add

docbook_xml_dtd_42

in this case _42 for the version in the error message 4.2, you may have to adjust the version.

[nh2]

Related to NixOS/nix#2979

[CMCDragonkai]

So I need all 3 deps in #77858