Fix pylint error
Fix pylint error

refs #9709

dschwen/moose,YaqiWang/moose,andrsd/moose,Chuban/moose,sapitts/moose,yipenggao/moose,liuwenf/moose,sapitts/moose,andrsd/moose,friedmud/moose,milljm/moose,nuclear-wizard/moose,laagesen/moose,YaqiWang/moose,harterj/moose,jessecarterMOOSE/moose,SudiptaBiswas/moose,bwspenc/moose,milljm/moose,SudiptaBiswas/moose,dschwen/moose,harterj/moose,harterj/moose,idaholab/moose,YaqiWang/moose,milljm/moose,idaholab/moose,laagesen/moose,harterj/moose,nuclear-wizard/moose,sapitts/moose,Chuban/moose,bwspenc/moose,jessecarterMOOSE/moose,YaqiWang/moose,lindsayad/moose,lindsayad/moose,yipenggao/moose,yipenggao/moose,harterj/moose,yipenggao/moose,permcody/moose,permcody/moose,jessecarterMOOSE/moose,jessecarterMOOSE/moose,lindsayad/moose,liuwenf/moose,dschwen/moose,sapitts/moose,laagesen/moose,permcody/moose,permcody/moose,friedmud/moose,laagesen/moose,friedmud/moose,bwspenc/moose,liuwenf/moose,sapitts/moose,bwspenc/moose,SudiptaBiswas/moose,Chuban/moose,lindsayad/moose,friedmud/moose,lindsayad/moose,Chuban/moose,dschwen/moose,andrsd/moose,idaholab/moose,milljm/moose,liuwenf/moose,jessecarterMOOSE/moose,liuwenf/moose,SudiptaBiswas/moose,SudiptaBiswas/moose,andrsd/moose,bwspenc/moose,idaholab/moose,dschwen/moose,idaholab/moose,nuclear-wizard/moose,milljm/moose,liuwenf/moose,laagesen/moose,nuclear-wizard/moose,andrsd/moose