Convert sets to lists for Python 3.
Convert sets to lists for Python 3.

landlab/landlab,csherwood-usgs/landlab,decvalts/landlab,amandersillinois/landlab,laijingtao/landlab,ManuSchmi88/landlab,SiccarPoint/landlab,cmshobe/landlab,ManuSchmi88/landlab,ManuSchmi88/landlab,RondaStrauch/landlab,amandersillinois/landlab,RondaStrauch/landlab,landlab/landlab,cmshobe/landlab,Carralex/landlab,SiccarPoint/landlab,laijingtao/landlab,Carralex/landlab,RondaStrauch/landlab,decvalts/landlab,csherwood-usgs/landlab,landlab/landlab,Carralex/landlab,cmshobe/landlab