When starting up GeoServer 2.12.0, it will log the message below for every non-workspaced style. In an environment with hundreds of styles, this causes the logs to be flooded with these messages. This can be fixed by modifying the fix for https://osgeo-org.atlassian.net/browse/GEOS-8289 to only apply to styles that have a workspace.
Failed to resolve workspace for style \"foo\". This means the workspace has not yet been added to the catalog, keep the proxy around"