refine appveyor.yml settings (#8254)
refine appveyor.yml settings (#8254)


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