message: Fix the lockfile-compat test
  The newest version of `tar` tweaks the checksum here slightly as the tarball is
  slightly different, so this just updates the test to pull the checksum from the
  publication rather than hardcoding it.
diff: @@ -79,9 +79,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
  #[test]
  fn frozen_flag_preserves_old_lockfile() {
  - Package::new("foo", "0.1.0").publish();
  + let cksum = Package::new("foo", "0.1.0").publish();
  - let old_lockfile =
  + let old_lockfile = format!(
  r#"[root]
  name = "zzz"
  version = "0.0.1"
  @@ -95,8 +95,10 @@ version = "0.1.0"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  [metadata]
  -"checksum foo 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f9e0a16bdf5c05435698fa27192d89e331b22a26a972c34984f560662544453b"
  -"#;
  +"checksum foo 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "{}"
  +"#,
  + cksum,
  + );
  let p = project("bar")
  .file("Cargo.toml", r#"
  @@ -109,7 +111,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
  foo = "0.1.0"
  "#)
  .file("src/lib.rs", "")
  - .file("Cargo.lock", old_lockfile)
  + .file("Cargo.lock", &old_lockfile)
  .build();
  assert_that(p.cargo("build").arg("--locked"),
  