On the Windows platform there will be some errors printed to the console if the user's thumbnail cache folder doesn't already exist. While creating those folders there is an attempt to do so multiple times and so we get errors when trying to create when exists. This is caused by paths that have hard-coded forward slashes, which causes our path processing routines to not work correctly. This patch defines those paths using platform-varying separator characters. Differential Revision: https://developer.blender.org/D11505 Reviewed by Brecht Van Lommel