[BUGFIX] Remove HTML from exception messages

Exception messages are independent from a specific context and thus
should not contain HTML code.

Resolves: #66344
Releases: master
Change-Id: I8bfab2d1da3fc3baf344d833eaaec8b267732baf
Reviewed-on: http://review.typo3.org/38609


Reviewed-by: Andreas Fernandez <andreas.fernandez@aspedia.de>
Tested-by: Andreas Fernandez <andreas.fernandez@aspedia.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>