Fix testcase for MPI_Accumulate() with MPI_PROC_NULL target rank
Fix testcase for MPI_Accumulate() with MPI_PROC_NULL target rank
pressel/mpi4py,mpi4py/mpi4py,pressel/mpi4py,mpi4py/mpi4py,mpi4py/mpi4py,pressel/mpi4py,pressel/mpi4py