Certain CI environments make it difficult or impossible to install all of
the dependencies needed to test Emborg.   This is common with two important
dependencies: Borg and Fuse.

Borg is needed for virtually all tests, so no accommodations are made for any 
testing if Borg is missing.

Fuse is needed by the mount and compare commands; it is used by Borg when 
mounting remote archives.

You can skip tests dependent on Fuse by defining the MISSING_DEPENDENCIES 
environment variable.  To do so, add the following lines to the tox.ini file:

    [testenv:pytest]
    setenv =                                 ← add
        MISSING_DEPENDENCIES = fuse          ← add
    commands = py.test -vv --cov {posargs}
