After accidentally running spread's autopkgtest, an error occurred with unbound variables. ``` ... Allocating ad-hoc ubuntu-16.04-amd64 /bin/bash: line 18: ADT_ARTIFACTS: unbound variable ... ``` Spread sets -u, which will causes incorrect behavior when checking against an unset variable: ``` $ set +u $ if [ -z "${unsetvariable}" ]; then echo "empty"; fi empty $ set -u $ if [ -z "${unsetvariable}" ]; then echo "empty"; fi bash: unsetvariable: unbound variable ``` Fix it by checking if set. ``` $ setvariable=set $ if [ -z "${setvariable:-}" ]; then echo "empty"; fi $ if [ -z "${unsetvariable:-}" ]; then echo "empty"; fi empty ``` Simply do the same for ADT_ARTIFACTS, and allow the check to happen as originally intended: ``` 2019-08-22 17:34:40 Allocating autopkgtest:ubuntu-16.04-amd64... 2019-08-22 17:34:40 Cannot allocate autopkgtest:ubuntu-16.04-s390x: adhoc only works inside autopkgtest ``` Signed-off-by: Chris Patterson <chris.patterson@canonical.com> - [ ] Have you followed the [guidelines for contributing](https://github.com/snapcore/snapcraft/blob/master/CONTRIBUTING.md)? - [ ] Have you signed the [CLA](http://www.ubuntu.com/legal/contributors/)? - [ ] Have you successfully run `./runtests.sh static`? - [ ] Have you successfully run `./runtests.sh tests/unit`? -----