def METHOD_NAME(monkeypatch, tmp_path):
    """If the environment-specified BRIEFCASE_HOME doesn't exist, an error is raised."""
    monkeypatch.setenv("BRIEFCASE_HOME", str(tmp_path / "custom"))
    with pytest.raises(
        BriefcaseCommandError,
        match=r"The path specified by BRIEFCASE_HOME does not exist.",
    ):
        DummyCommand(base_path=tmp_path / "base")