ASSERT FAILED calling setTransactionIsolation checking isolation_ == level on pooled connection

For DERBY-4314, I thought I would do a little testing to understand the server round trips in various scenarios for pooled connections. So I wrote the small attached program ConnReuse.java and hit this assertion in client:

Exception in thread "main" org.apache.derby.shared.common.sanity.AssertFailure: ASSERT FAILED
at org.apache.derby.shared.common.sanity.SanityManager.ASSERT(SanityManager.java:98)
at org.apache.derby.client.am.Connection.setTransactionIsolationX(Connection.java:987)
at org.apache.derby.client.am.Connection.setTransactionIsolation(Connection.java:915)
at org.apache.derby.client.am.LogicalConnection.setTransactionIsolation(LogicalConnection.java:253)
at TestConnReuse.main(TestConnReuse.java:32)
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To run the program on trunk:
java org.apache.derby.drda.NetworkServerControl start
java TestConnReuse.

This needs more investigation, but I thought I would go ahead and log the bug. I tried this only on trunk. I have not yet

• Tried it on the branches.
• Tried it with Lily's DERBY-4314 patch.
• Tried it with embedded.
• Tried actually doing something with the prior logical connection which might be related.