BuildStream throws an exception on Linux when fuse is unavailable

Summary

When running on a Linux machine without fuse, BuildStream currently throws an exception. (Technically, it's the fuse library throwing it, and BuildStream is failing to suppress it.)

An example of this can be found in this CI job for bst-plugins-container repository. That CI environment isn't expected to have fuse, since it doesn't contain plugins that require it. It used to work fine until 2 days ago.

What is the expected correct behavior?

BuildStream doesn't throw an exception when fuse is unavailable.