TODO this is less efficient on python2

In PyQt5.6, connect() does strict checking of the signal signature
against the Slot decorator types, so "@slot(object)" is not a catch-all
anymore.

[qflatboob] load all fields in widget list (this will help to correctly rank adverts) / Add an url field

flake8 --select E713, semi-manual fixing

Remove useless trailing \
Remove trailing spaces
Add missing empty lines

autopep8 -ir -j2 --select=E301,E302,E502,W291,W293,W391 .

Diff quickly checked.

autopep8 -ir -j2 --select=E303,E125
Diff checked manually.