replace use of return_future with gen.coroutine (#8135)
replace use of return_future with gen.coroutine (#8135)


jakirkham/bokeh,stonebig/bokeh,stonebig/bokeh,stonebig/bokeh,jakirkham/bokeh,mindriot101/bokeh,dennisobrien/bokeh,dennisobrien/bokeh,ericmjl/bokeh,jakirkham/bokeh,timsnyder/bokeh,bokeh/bokeh,bokeh/bokeh,ericmjl/bokeh,jakirkham/bokeh,ericmjl/bokeh,ericmjl/bokeh,stonebig/bokeh,timsnyder/bokeh,mindriot101/bokeh,mindriot101/bokeh,mindriot101/bokeh,bokeh/bokeh,timsnyder/bokeh,dennisobrien/bokeh,dennisobrien/bokeh,ericmjl/bokeh,jakirkham/bokeh,timsnyder/bokeh,timsnyder/bokeh,bokeh/bokeh,dennisobrien/bokeh,bokeh/bokeh