add DESI_LOGLEVEL environment variable, add doc, define WARNING... in module
add DESI_LOGLEVEL environment variable, add doc, define WARNING... in module

timahutchinson/desispec,gdhungana/desispec,timahutchinson/desispec,profxj/desispec,profxj/desispec,gdhungana/desispec,desihub/desispec,desihub/desispec