Error in running DBT2

I am using centOS6 and after all confugration, I run the below command

dbt2-run-workload -a pgsql -d 120 -w 1 -o /tmp/result -c 10

Error:
Stage 3. Processing of results...
Killing client...
waiting for server to shut down.... done
server stopped
Traceback (most recent call last):
  File "/tmp/dbt2/bin/dbt2-post-process", line 14, in <module>
    import rpy2.robjects as robjects
ImportError: No module named rpy2.robjects
Test completed.
Results are in: /tmp/result

Please guide me !! :)