narval #3553531 Improve logs display [validation pending]

Make error messages more robust and easily display them to the users.

prioritynormal
typeenhancement
done in4.0.0
load1.000
load left0.000
closed by#1fa5c5e3c859 [logformat] Insert newline when unfolding traceback (closes #3553531)
patch[logformat] Insert newline when unfolding traceback (closes #3553531) [applied][view] make logformat.py a bit more robust (related to #3553531) [applied][views] use <div> instead of <pre> when formatting logs (related to #3553531) [applied][views] split log_to_html and add severities parameter to facilitate code reuse (related to #3553531) [applied]