[infra-tests] Stability script: normalize results format (#5330)

The "check stability" script parses test results into a List of tuples.
Later operations expect the fourth element to be a (possibly empty) List
of "messages". While this expectation is satisfied when the instability
is the result of a subtest's behavior, the parsing operation previously
violated the contract when interpreting test failures.

Update the parsing logic to provide an empty List in cases where a test
(rather than a subtest) is the source of instability.

View on GitHub: https://github.com/w3c/web-platform-tests/pull/5330

Received on Monday, 3 April 2017 19:33:03 UTC