ERROR: MadAnalysis5 failed to create PDF output

Dear Oliver,
     I want to use MG5_aMC for calculations of some hadronic processes.But the terminal always output error.
     Here is what I get
##################################
INFO: Idle: 0, Running: 0, Completed: 0 [ current time: 16h50 ]
INFO: Idle: 0, Running: 0, Completed: 0 [ current time: 16h50 ]
INFO: Combining runs
INFO: finish refine
INFO: Combining Events
  === Results Summary for run: test tag: tag_1 ===

     Cross-section : 79.7 +- 0.1099 pb
     Nb of events : 50000

fail
Failed to access python version of LHAPDF: If the python interface to LHAPDF is available on your system, try adding its location to the PYTHONPATH environment variable and theLHAPDF library location to LD_LIBRARY_PATH (linux) or DYLD_LIBRARY_PATH (mac os x).
INFO: can not run systematics since can not link python to lhapdf
store_events
INFO: Storing parton level results
INFO: End Parton
reweight -from_cards
decay_events -from_cards
INFO: Running MadAnalysis5 [arXiv:1206.1599]
INFO: Parton input file considered:
INFO: --> /home/wangbin/work/Mg5_aMC/LHC14_SM/pptotltl/Events/test/unweighted_events.lhe.gz
INFO: MadAnalysis5 now running the 'analysis1' analysis...
INFO: Follow Madanalysis5 run with the following command in a separate terminal:
INFO: tail -f /home/wangbin/work/Mg5_aMC/LHC14_SM/pptotltl/Events/test/tag_1_MA5_analysis1.log
ERROR: MadAnalysis5 failed to create PDF output
INFO: MadAnalysis5 successfully completed the analysis 'analysis1'. Reported results are placed in:
INFO: --> /home/wangbin/work/Mg5_aMC/LHC14_SM/pptotltl/Events/test/tag_1_MA5_parton_analysis_analysis1.pdf
INFO: Finished MA5 analyses.
Command "launch test" interrupted with error:
KeyError : 'mg5amc_py8_interface_path'
Please report this bug on https://bugs.launchpad.net/mg5amcnlo
More information is found in '/home/wangbin/work/Mg5_aMC/LHC14_SM/pptotltl/test_tag_1_debug.log'.
Please attach this file to your report.
INFO: storing files of previous run
INFO: Done
INFO:
quit
INFO:
#################
What is the reason for this problem?

Thanks,
BinW