Specify where the code is coming from as the URL

Summary:
Makes it much simpler to see where warnings are coming from if we get to
see a file name.

Test Plan: Fixed a warning with it

Reviewers: Kirigami, mart

Reviewed By: Kirigami, mart

Subscribers: mart, plasma-devel

Tags: Kirigami

Differential Revision: https://phabricator.kde.org/D26628