Styling regression: form validation errors

[Thomas De Schampheleire]

Hi Mads,

A recent commit of yours:
changeset:   6920:35d3a85fc650
user:        Mads Kiilerich <mads at kiilerich.com>
date:        Sun Jun 11 15:02:09 2017 +0200
summary:     style: use plain Bootstrap with existing CSS styling

seems to have (unintentionally?) broken some styling. In particular,
form validation errors (class 'error-message') are no longer shown in
red.

I haven't checked things exhaustively, just bumped into that
difference so I report it.

Best regards,
Thomas