
For versions of aws-parallelcluster >= 2.9, the pyyaml dependency had to be >= 5.3.1 and == 5.1.2
at the same time making impossible to install ParallelCluster >= 2.9 from spack repository.
See issue: https://github.com/spack/spack/issues/28172
Fixed by limiting pyyaml 5.1.2 version to aws-parallelcluster < 2.8, according to this commit:
7255d314b7
Tested with a manual installation of aws-parallelcluster@2.11.4