[debug-toolbar/fix] only import mako when the toolbar is loaded

[pkg] require logilab-common >= 1.5.2 Followup a902521

[web/views] Fix AutoformSectionRelationTags.set_muledit_editable It is a method call, so `self` is passed implicitely as first argument, so it is useless to pass it also explicitely as second argument. In fact, it does not work without this. A monkey patch had been done in a private client's project, but the fix is revelant for everyone.