attempt to run INSCHEK for each instruction file, model output
    file pair in a pyemu.Pst.  If the run is successful, the INSCHEK written
    .obf file is used to populate the pst.observation_data.obsval attribute

    Parameters
    ----------
    pst : (pyemu.Pst)

def try_run_inschek(pst):
    """ attempt to run INSCHEK for each instruction file, model output
    file pair in a pyemu.Pst.  If the run is successful, the INSCHEK written
    .obf file is used to populate the pst.observation_data.obsval attribute

    Parameters
    ----------
    pst : (pyemu.Pst)

    """
    for ins_file,out_file in zip(pst.instruction_files,pst.output_files):
        df = _try_run_inschek(ins_file,out_file)
        if df is not None:
            pst.observation_data.loc[df.index, "obsval"] = df.obsval