Backport PR #28614 on branch 0.25.x (CI: troubleshoot s3fs failures)
Backport PR #28614: CI: troubleshoot s3fs failures
Not sure what is up with py36 failure. If someone has time to debug would certainly be welcome Failure is in read_parquet, traceback goes to a .pxi file in pyarrow and ends with "???" which usually means its in C.  cc @jorisvandenbossche  That's a know problem for certain versions of fastparquet, we skip those tests on master, but should probably backport that skip: https://github.com/pandas-dev/pandas/pull/28357 Triggered backport: https://github.com/pandas-dev/pandas/pull/28627
 I restarted the failed builds, and now all green, so merging