0.8 test fails with 'duplicity not found' errors

[Sebastien Bacher]

Trying to get duplicity updated in Debian/Ubuntu, on the Debian request (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=929949) the maintainer wrote

'yes. so far i can't make duplicity 0.8.0 work with python 2.7 which is still
the default version in debian and hence important in my opinion.
(by "does not work" i mean: the built-in test suite fails quite a lot'

Trying on Ubuntu Disco to see how it behave the tests fail with a

$ cd /tmp
$ bzr branch lp:duplicity
$ cd duplicity
$ python2.7 setup.py build --force
$ PYTHONPATH=/tmp/duplicity/build/lib.linux-i686-2.7/ python2.7 ./setup.py test
(that's on an i386 chroot, path to adapt for amd64)
...
======================================= test session starts =======================================
platform linux2 -- Python 2.7.16, pytest-4.6.3, py-1.8.0, pluggy-0.12.0
rootdir: /build/duplicity, inifile: tox.ini, testpaths: testing/unit, testing/functional
collected 438 items
...
-------------------------------------- Captured stderr call ---------------------------------------

...command: "setsid" "-w" "duplicity" "full" "testfiles/select2" "file://testfiles/output" "--volsize" "1" "--exclude-filelist=testfiles/exclude.txt" "-v0" "--no-print-statistics" "--allow-source-mismatch" "--archive-dir=testfiles/cache" < /dev/null
...cwd: /build/duplicity/testing
...output:
setsid: failed to execute duplicity: No such file or directory
...return_val: 1

(the same error is hit using python3.7)

[Sebastien Bacher (seb128)]

(sorry duplicate report)