fixed failing test on python3.5
fixed failing test on python3.5

ultimate-pa/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,dbeyer/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,dbeyer/benchexec,ultimate-pa/benchexec,dbeyer/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,dbeyer/benchexec