Warning when building man pages

Hi,

I get a warning when building the man pages on Debian testing. The
warning is in the documentation for CREATE POLICY and as caused by the
three footnotes in the sql-createpolicy-summary table.

I do not understand our documentation pipeline well enough to know what
the proper fix would be.

Error message:

Element sup in namespace '' encountered in a, but no template matches.
Element sup in namespace '' encountered in a, but no template matches.
Element sup in namespace '' encountered in a, but no template matches.
Note: Writing man7/CREATE_POLICY.7

Package versions:

docbook 4.5-6
docbook-dsssl 1.79-9.1
docbook-xml 4.5-8
docbook-xsl 1.79.1+dfsg-2
openjade 1.4devel1-21.3+b1
opensp 1.5.2-13+b1
xsltproc 1.1.29-5

Andreas