Pin attrs to not pull in vers. w/ deprecation affecting pytest. (#18257)
Pin attrs to not pull in vers. w/ deprecation affecting pytest. (#18257)

(sapling split of e5ddb6bc46a246659bcdcfda4a3c4e897e012131)
foursquare/fsqio,foursquare/fsqio,foursquare/fsqio,foursquare/fsqio,foursquare/fsqio