change _of_ to _at_ in divergence.py
change _of_ to _at_ in divergence.py

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