Add proper error message when invalid BOKEH_LOG_LEVEL (#7276) (#7277)
Add proper error message when invalid BOKEH_LOG_LEVEL (#7276) (#7277)


ericmjl/bokeh,jakirkham/bokeh,dennisobrien/bokeh,aavanian/bokeh,jakirkham/bokeh,bokeh/bokeh,jakirkham/bokeh,timsnyder/bokeh,aavanian/bokeh,Karel-van-de-Plassche/bokeh,Karel-van-de-Plassche/bokeh,aavanian/bokeh,bokeh/bokeh,bokeh/bokeh,Karel-van-de-Plassche/bokeh,timsnyder/bokeh,aavanian/bokeh,aavanian/bokeh,stonebig/bokeh,mindriot101/bokeh,timsnyder/bokeh,jakirkham/bokeh,mindriot101/bokeh,timsnyder/bokeh,dennisobrien/bokeh,stonebig/bokeh,dennisobrien/bokeh,ericmjl/bokeh,bokeh/bokeh,Karel-van-de-Plassche/bokeh,timsnyder/bokeh,dennisobrien/bokeh,ericmjl/bokeh,Karel-van-de-Plassche/bokeh,ericmjl/bokeh,bokeh/bokeh,stonebig/bokeh,mindriot101/bokeh,mindriot101/bokeh,jakirkham/bokeh,dennisobrien/bokeh,ericmjl/bokeh,stonebig/bokeh