In looking at the methods set in the session in session_api.c:wt_open_session I noticed that in the list of functions in stds_readonly it sets session_flush_tier. A call to flush_tier should not be supported on read-only connections.

The change needed is:

• Set that to a (new function) session_flush_tier_readonly
• Create the new function session_flush_tier_readonly (look for many other readonly examples of functions there)
• Likely add a new statistic for a failed call (possibly add it to the error path of session_flush_tier as well.
• Write a python test that calls flush_tier on a readonly connection and verify the error (test should fail prior to this work as current develop allows this).