[gw2] linux -- Python 3.7.3 /home/becky/buildstream/.tox/py37/bin/python

cli = <buildstream.testing.runcli.CliIntegration object at 0x7f4df9735c18>
datafiles = local('/home/becky/buildstream/.tox/py37/tmp/popen-gw2/test_host_files_missing_option0')
optional = 'optional'

    @pytest.mark.parametrize("optional", [("mandatory"), ("optional")])
    @pytest.mark.datafiles(DATA_DIR)
    @pytest.mark.skipif(not HAVE_SANDBOX, reason='Only available with a functioning sandbox')
    def test_host_files_missing(cli, datafiles, optional):
        project = str(datafiles)
        ponyfile = os.path.join(project, 'files', 'shell-mount', 'horsy.txt')

        option = (optional == "optional")

        # Assert that we did successfully run something in the shell anyway
        result = execute_shell(cli, project, ['echo', 'Hello'], config={
            'shell': {
                'host-files': [
                    {
                        'host_path': ponyfile,
                        'path': '/etc/pony.conf',
>                       'optional': option
                    }
                ]
            }
        })

tests/integration/shell.py:260:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
tests/integration/shell.py:41: in execute_shell
    project=project, project_config=config, args=['build', element])
src/buildstream/testing/runcli.py:563: in run_project_config
    base_config = _yaml.load_data(config)
src/buildstream/_yaml.pyx:407: in buildstream._yaml.load_data
    cpdef Node load_data(str data, int file_index=_SYNTHETIC_FILE_INDEX, str file_name=None, bint copy_tree=False):
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

>   f_info = <FileInfo> _FILE_LIST[file_index]
E   IndexError: list index out of range

src/buildstream/_yaml.pyx:440: IndexError