Hi,
these are all the warning I've found in your log file; they all seem fine to me, so I wouldn't worry about them.
Marco
$ grep WARNING ductape_nb.log
2019-05-22 13:06:24 - ductape.kegg - [WARNING] - Using RCLASS attribute of KEGG reactions, as the RPAIR database has now been discontinued
2019-05-22 13:22:04 - ductape.kegg - [WARNING] - Using RCLASS attribute of KEGG reactions, as the RPAIR database has now been discontinued
2019-05-22 13:28:27 - ductape.kegg - [WARNING] - Using RCLASS attribute of KEGG reactions, as the RPAIR database has now been discontinued
2019-05-22 13:29:42 - ductape.kegg - [WARNING] - Using RCLASS attribute of KEGG reactions, as the RPAIR database has now been discontinued
2019-05-22 13:30:15 - ductape.biolog - [WARNING] - YAML/OPM parsing failed!
2019-05-22 13:30:32 - ductape - [WARNING] - Activity index has not been calculated yet!
2019-05-22 13:30:32 - ductape - [WARNING] - Skipping Kegg mapping
2019-05-22 13:30:47 - ductape.kegg - [WARNING] - Using RCLASS attribute of KEGG reactions, as the RPAIR database has now been discontinued
2019-05-22 13:30:50 - ductape.kegg - [WARNING] - Using RCLASS attribute of KEGG reactions, as the RPAIR database has now been discontinued
2019-05-22 14:01:34 - ductape - [WARNING] - No compounds available for category nitrogen (ecoli25922)
2019-05-22 14:01:34 - ductape - [WARNING] - No compounds available for category phosphate & sulphur (ecoli25922)
2019-05-22 14:01:34 - ductape - [WARNING] - No compounds available for category nutrient stimulation (ecoli25922)
2019-05-22 14:01:34 - ductape - [WARNING] - No compounds available for category nitrogen peptides (ecoli25922)
2019-05-22 14:01:34 - ductape - [WARNING] - No compounds available for category osmolytes & ph (ecoli25922)
2019-05-22 14:01:39 - ductape - [WARNING] - No compounds available for category chemicals (ecoli25922)