Dear Oliver,
I reinstall pythia8 successfully.But when I run the file of pptotltl.txt,the terminal output error.
Here is what I get,
#########################
:~/work/Mg5_aMC$ ./bin/mg5_aMC pptotltl.txt
..........
INFO: need to improve 0 channels 
Current estimate of cross-section: 79.7882414504 +- 0.12059282085
    P2_gg_ttxgg_t_wpb_wp_lvl_tx_wmbx_wm_lvl 
    P2_gg_ttxqq_t_wpb_wp_lvl_tx_wmbx_wm_lvl 
    P2_gq_ttxgq_t_wpb_wp_lvl_tx_wmbx_wm_lvl 
    P2_qq_ttxqq_t_wpb_wp_lvl_tx_wmbx_wm_lvl 
    P2_qq_ttxgg_t_wpb_wp_lvl_tx_wmbx_wm_lvl 
    P1_gg_ttxg_t_wpb_wp_lvl_tx_wmbx_wm_lvl 
    P1_gq_ttxq_t_wpb_wp_lvl_tx_wmbx_wm_lvl 
    P1_qq_ttxg_t_wpb_wp_lvl_tx_wmbx_wm_lvl 
    P0_gg_ttx_t_wpb_wp_lvl_tx_wmbx_wm_lvl 
    P0_qq_ttx_t_wpb_wp_lvl_tx_wmbx_wm_lvl 
INFO:  Idle: 0,  Running: 0,  Completed: 0 [ current time: 17h49 ] 
INFO:  Idle: 0,  Running: 0,  Completed: 0 [ current time: 17h49 ] 
INFO: Combining runs 
INFO: finish refine 
INFO: Combining Events 
  === Results Summary for run: run_01 tag: tag_1 ===

     Cross-section :   79.79 +- 0.1206 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/run_01/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/run_01/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/run_01/tag_1_MA5_parton_analysis_analysis1.pdf 
INFO: Finished MA5 analyses. 
INFO: Running Pythia8 [arXiv:1410.3012] 
No user-defined value for Pythia8 parameter 'JetMatching:nJetMax'. Setting it automatically to 2.
Splitting .lhe event file for PY8 parallelization...
Submitting Pythia8 jobs...
Pythia8 shower jobs: 0 Idle, 4 Running, 0 Done [1m50s]
Pythia8 shower jobs: 0 Idle, 0 Running, 4 Done [1h13m02s]
Merging results from the split PY8 runs...
[Errno 28] No space left on device
Command "generate_events run_01" interrupted with error:
IOError : [Errno 28] No space left on device
Please report this bug on https://bugs.launchpad.net/mg5amcnlo
More information is found in '/home/wangbin/work/Mg5_aMC/LHC14_SM/pptotltl/run_01_tag_1_debug.log'.
Please attach this file to your report.
INFO: storing files of previous run 
INFO: Done 
ERROR: I/O error (28): No space left on device 
INFO:  
ln: 无法创建符号链接'ME5_debug': 设备上没有空间
INFO:  
quit
INFO:  
more information in /home/wangbin/work/Mg5_aMC/LHC14_SM/pptotltl/index.html
quit
######################
It seems like former error.
thanks,
BinW