Following the RCN calibration found on the wiki [https://wiki.apertus.org/index.php/Factory_Calibration_(firmware_2.0) ], this bug rise :
AttributeError: module 'png' has no attribute 'read_pnm_header'
(see the wiki for full error)
The idea discussed on IRC (21st feb 2020, 22h50) was to update the rcn_darkframe.py in order to adapt to the new pypng structure (ie " "pripngtopam command line tool converts PNG to NetPBM PNM/PAM file. Previously png.py did this." ).