def packages_yaml_v015(tmpdir):
    """Return the path to an existing manifest in the v0.15.x format
    and the path to a non yet existing backup file.
    """
    raw_yaml = """
spack:
  specs:
  - mpich
  packages:
    cmake:
      paths:
        cmake@3.17.3: /usr
"""
    manifest = tmpdir.ensure('spack.yaml')
    backup_file = tmpdir.join('spack.yaml.bkp')
    manifest.write(raw_yaml)
    return manifest, backup_file