d28b885f7a
When juju 3.x is used (installed from a snap in strict confinement) the temporary directory of the system (e.g. /tmp) can't be read by 'juju', this is used by zaza-openstack-tests to write testing policy files among other transitory files that are passed to juju's CLI. This change moves Python's default temporary file to ~/tmp unless overriden by the environment variable TEST_TMPDIR.