message: Update chrono to 0.4.20, avoiding RUSTSEC-2020-0159
  See:
diff: @@ -306,12 +306,11 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
  [[package]]
  name = "chrono"
  -version = "0.4.19"
  +version = "0.4.20"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  -checksum = "670ad68c9088c2a963aaa298cb369688cf3f9465ce5e2d4ca10e6e0098a1ce73"
  +checksum = "6127248204b9aba09a362f6c930ef6a78f2c1b2215f8a7b398c06e1083f17af0"
  dependencies = [
  "js-sys",
  - "libc",
  "num-integer",
  "num-traits",
  "wasm-bindgen",
  