Test suite fails when run from within a directory with spaces in its name

When the test suite is run under 'strace -f -e trace=process ./test' inside a directory with spaces in it, it fails because of improper argument splitting:

[pid 440] execve("/var/lib/jenkins/jobs/juju", ["/var/lib/jenkins/jobs/juju", "tests/workspace/bin/relation-get", "--format=json", "-", "mysql/0"], [/* 9 vars */]) = -1 ENOENT (No such file or directory)