Toaster looks for and will include the optional fixture file "custom.xml". The test for this file relied on a passive fail if that file was not fount, but now it is a hard fail that breaks Toaster startup. The solution is to wrap the load command with a "try" and passive "except" (rather than for example trying to guess and test the path to that file).
(Bitbake rev: 132458939d3987ebc58685397714af3d6d5cd8fd)