Bug#880210: installation-guide: validity errors when building the manual

[Cyril Brulebois <kibi@debian.org>]

Package: installation-guide
Severity: important

Hi,

Since dillon's upgrade to stretch, new errors can be seen while
building the manual from SVN.

We were already having a lot of such lines:
> found empty tag para

Now we've got those as well (excerpt):
| /home/d-i/trunk/manual/en/preparing/bios-setup/arm.xml:5: element sect2: validity error : ID boot-dev-select already defined
|   <sect2 arch="arm64" id="boot-dev-select"><title>Boot Device Selection</title>
|                                           ^
| /home/d-i/trunk/manual/en/boot-installer/x86.xml:4: element sect2: validity error : ID usb-boot already defined
|   <sect2 arch="any-x86" condition="bootable-usb" id="usb-boot">
|                                                               ^
| /home/d-i/trunk/manual/en/boot-installer/x86.xml:257: element sect2: validity error : ID boot-tftp already defined
|   <sect2 arch="x86" id="boot-tftp"><title>Booting with TFTP</title>
|                                   ^
| /home/d-i/trunk/manual/en/boot-installer/x86.xml:464: element footnote: validity error : ID gtk-miniiso already defined
| image is available<footnote id="gtk-miniiso">

This seems to be trivially reproducible by calling ./buildone.sh from
the build directory, from an SVN manual checkout.

Help welcome!


KiBi.