something about DISPLAY in /core/utils.py

I have just finished (ultimately successful) the installation of tupak on the CNAF cluster in Bologna. The operating system right now is Scientific Linux 6.9. The main work was really to install Python (3.6.6) with tkinker and bz2 without root rights, but at the very end, a problem remained when trying to import tupak, which I could only solve by modifying tupak code.

There must have been a recent change of the final lines in /core/utils.py concerning the DISPLAY, which produced some errors when I tried importing tupak. I changed these lines to an older version and it worked. Here the older version that I used to substitute the latest one:

command_line_args = set_up_command_line_arguments()

if 'DISPLAY' in os.environ:
    pass
else:
    logging.info('No $DISPLAY environment variable found, so importing \
                  matplotlib.pyplot with non-interactive "Agg" backend.')
    import matplotlib
    matplotlib.use('Agg')

I assume that the latest version of tupak runs on some Linux system, so the problem is maybe a combination of tupak and my operating system / local Python installation. Any idea whether I could have solved the problem without modifying tupak code?