It's not possible to disable the progress bar of delphin process

[goodmami]

The progress bar displayed when running delphin process is handled all the way in TestSuite.process(), and there's no option to turn it off. It can, in fact, be disabled if the logging level is at INFO or DEBUG, but then per-item information is printed. Applications that make use of the process command or method (such as the Matrix's regression test; see delph-in/matrix#479) may want to disable it so they can do their own reporting.