message: Ubuntu 16.04 is no longer available
diff: @@ -139,7 +139,6 @@ jobs:
  fail-fast: false
  matrix:
  include:
  - - {ubuntu: 16.04, mpi: serial, rust: nightly}
  - {ubuntu: 18.04, mpi: mpich, rust: beta}
  - {ubuntu: 20.04, mpi: openmpi, rust: stable}
  steps:
  