fix tox regression / incompatible change
tests are broken for tox 3.2.x .. 3.4.0 versions:
/home/travis/build/borgbackup/borg/.tox/py34/bin/python: Error while
finding spec for 'borg.archiver' (<class 'ImportError'>: No module
named 'borg')
we see this breakage only on 1.0-maint branch, 1.1-maint is fine.
1.1-maint uses the src/ code layout, 1.0-maint does not. related?
Thomas Waldmann