The test is a bit primitive as it checks the Bitcoin Core log and
assumes that if it logs that it creates a transient session, then it
does that indeed.
A more thorough test would be to check that it indeed sends the
`SESSION CREATE ... DESTINATION=TRANSIENT` command and that it uses
the returned I2P address for connecting, even for repeated connections
to the same I2P peer. That would require a mocked SAM server (proxy)
implementation in Python.
