troubleshoot CI failing Linux py36_32bit
closes #28829
@TomAugspurger there's probably a reason pytest was pinned. if not successful we should add attrs to dependencies and pin attrs? ok so the pytest pin makes no difference. pytest 4.0.2 installed. so pytest is now running. merge on green? @pandas-dev/pandas-core  this is ok FYI, these CI fixups should typically be backported. Doing so in https://github.com/pandas-dev/pandas/pull/28999.