Comment 1 for bug 1833573

Those changes create issue when building with python3 on an env where python is python2 it looks like...

$ cd /tmp
$ bzr branch lp:duplicity
$ cd duplicity
$ bzr revno
1389
$ python3.7 setup.py build --force
$ PYTHONPATH=/tmp/duplicity/build/lib.linux-i686-3.7/ python3.7 ./setup.py test
(that's on an i386 chroot, path to adapt for amd64)

ends up with that error

b' File "/build/duplicity/duplicity/librsync.py", line 33, in <module>'
b' from . import _librsync'
b'ImportError: cannot import name _librsync'

which is because bin/duplicity uses python2 but the .so is built for python3 only in that scenario