No error message for missing config file

[bcaddy]

If you try to run Cholla with a non-existent config file you get complex PMIx errors instead of just a error message. There should be some checking that a config file exists and that it has the proper info. C++17 makes this much easier with std::filesystem.

Example:

rcaddy@c3po:bin$ mpirun -n 4 ./cholla.hydro.c3po ./sod512.txt
No protocol specified
Git Commit Hash = 646614bd94fd580c2b09a2a11a1e7a9c488427bd
Macro Flags     = -DCUDA -DMPI_CHOLLA -DPRECISION=2 -DPPMC -DHLLC -DSIMPLE -DDENSITY_FLOOR -DTEMPERATURE_FLOOR -DOUTPUT -DHDF5 -DGIT_HASH=646614bd94fd580c2b09a2a11a1e7a9c488427bd
Parameter values:  nx = 0, ny = 0, nz = 0, tout = 0.000000, init = , boundaries = 0 0 0 0 0 0
Output directory:  pRs���

Creating Log File: run_output.log

nproc_x 2 nproc_y 2 nproc_z 1
Allocating MPI communication buffers on GPU (nx = 0, ny = 0, nz = 1280).
--------------------------------------------------------------------------
MPI_ABORT was invoked on rank 3 in communicator MPI_COMM_WORLD
with errorcode -1.

NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes.
You may or may not see output from other processes, depending on
exactly when Open MPI kills them.
--------------------------------------------------------------------------
[c3po:912606] PMIX ERROR: UNREACHABLE in file ../../../src/server/pmix_server.c at line 2193
[c3po:912606] PMIX ERROR: UNREACHABLE in file ../../../src/server/pmix_server.c at line 2193
[c3po:912606] PMIX ERROR: UNREACHABLE in file ../../../src/server/pmix_server.c at line 2193
Local number of grid cells: 0 0 0 512
Setting initial conditions...
ABORT: : Unknown initial conditions!
[c3po:912606] 3 more processes have sent help message help-mpi-api.txt / mpi-abort
[c3po:912606] Set MCA parameter "orte_base_help_aggregate" to 0 to see all help / error messages