Cannot adjust line warning in generated man page

During work on Debian package of khal 0.9.2 I hit warning about man page which can be reproduced easily:

LC_ALL=3Den_US.UTF-8 MANROFFSEQ=3D'' MANWIDTH=3D80 man --warnings -E UTF-8 =
-l -Tutf8 -Z build/man/khal.1 >/dev/null

resulting in:

<standard input>:101: warning [p 1, 9.7i]: cannot adjust line
<standard input>:1424: warning [p 14, 2.7i]: cannot adjust line

First line that cannot be adjusted is reference to python's str.format which can be simply removed but second one is from generated rst file (default option of one config parameter).

Unfortunately I wasn't able to find out why this is happening. Workaround is
eg. to add .nf before affected paragraph to avoid wrapping it.
But I didn't find out (by even digging into sphinx.writer.manpage code and khal's config generator) how to force Sphinx to do so - it may be a bug in Sphinx manpage generator as well but this error didn't happen with khal 0.8.x.

Reproduce the warning with the command shown against build/man/khal.1, then inspect the referenced Sphinx manpage writer and khal's config generator. Determine why the two affected paragraphs cannot be adjusted and confirm the generated man page completes without these warnings while preserving the documented text.