The rate-limit branch added by the original PR did sleep+continue with
no attempt to record the last error, so persistent iLink -2 responses
exhausted the retry loop and hit 'assert last_error is not None',
raising AssertionError instead of a descriptive RuntimeError.
Record last_error = RuntimeError(...) before continuing, and break out
of the loop on the final attempt instead of sleeping uselessly.
c69310c625