fix bug where presigned urls weren't generating because of exceeding expiration threshold
fix bug where presigned urls weren't generating because of exceeding expiration threshold

UM-USElab/gradecraft-development,UM-USElab/gradecraft-development,mkoon/gradecraft-development,UM-USElab/gradecraft-development,mkoon/gradecraft-development,UM-USElab/gradecraft-development,mkoon/gradecraft-development