fix https://github.com/sagemathinc/smc/issues/1728 -- jupyter notebook save exception -- part 2
fix https://github.com/sagemathinc/smc/issues/1728 -- jupyter notebook save exception -- part 2

sagemathinc/smc,tscholl2/smc,tscholl2/smc,sagemathinc/smc,DrXyzzy/smc,tscholl2/smc,DrXyzzy/smc,sagemathinc/smc,tscholl2/smc,tscholl2/smc,DrXyzzy/smc,DrXyzzy/smc,sagemathinc/smc