Fix typo in exceptions.md
Fix typo in exceptions.md

yunstanford/sanic,ashleysommer/sanic,channelcat/sanic,yunstanford/sanic,yunstanford/sanic,channelcat/sanic,channelcat/sanic,yunstanford/sanic,lixxu/sanic,lixxu/sanic,ashleysommer/sanic,channelcat/sanic,lixxu/sanic,lixxu/sanic,ashleysommer/sanic