doc-base: some errors reported during postinstall

[Vasya Pupkin]

I just noticed this when installed some package that installed doc-base as a dependency:

Setting up doc-base (0.10.7) ...
Registering 16 doc-base files...
Error in `/usr/share/doc-base/xapian-python3-docs', line 9: all `Format' sections are invalid.
Note: `install-docs --verbose --check file_name' may give more details about the above error.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: doc-base 0.10.7
ProcVersionSignature: Ubuntu 4.4.0-119.143-generic 4.4.114
Uname: Linux 4.4.0-119-generic i686
ApportVersion: 2.20.1-0ubuntu2.16
Architecture: i386
Date: Fri Apr 13 15:45:33 2018
InstallationDate: Installed on 2011-11-13 (2342 days ago)
InstallationMedia: Ubuntu-Server 10.04.3 LTS "Lucid Lynx" - Release i386 (20110719.2)
PackageArchitecture: all
SourcePackage: doc-base
UpgradeStatus: Upgraded to xenial on 2017-09-21 (204 days ago)