python: add details on missing library to error message (#9332)
python: add details on missing library to error message (#9332)

When a library cannot be found, the exception now includes the name
of the library that was requested.
iulian787/spack,iulian787/spack,LLNL/spack,LLNL/spack,iulian787/spack,LLNL/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack