Not sure I completely understand this yet, so opening an issue for now:

After #5677, I believe it is now the case that the rpc tests may fail if there's inactivity for more than 30 seconds after opening a connection. I'm getting repeatable failures locally on some of the longer-running tests (such as bipdersig.py), which I seem to be able to fix by either increasing the rpctimeout on all the nodes in the test, or by keeping the rpc connections warm with more rpc calls.

I think some travis jobs may be failing for this reason as well: https://travis-ci.org/bitcoin/bitcoin/builds/79514930

I'm not sure what the right solution is -- should the rpc test framework change somehow to allow for the connection to be re-established? Or should we just be defaulting the timeout to a longer value in the tests that need it?