In order to troubleshoot my Python Gstreamer app, I cloned and added some debug statements to the Gstreamer core. Now I want Python to load my private build of gstreamer, instead of the standard one in /usr/local/lib/gstreamer-1.0/. For the Gstreamer core, I modified LD_LIBRARY_PATH, but this has no effect. For the record, I'm running on 3.13.0-91-generic #138-Ubuntu.
I was able to do something similar for Gstreamer plugins using the env var GST_PLUGIN_PATH. I suspect that Gobject may use it's own environment variable to load libraries, but I haven't found it.