9 files declare their use of PromiseInterface in Zircon Profile 8.0

ClientInterface.php in vendor/guzzlehttp/guzzle/src/ClientInterface.php

EachPromiseTest.php in vendor/guzzlehttp/promises/tests/EachPromiseTest.php

MockHandler.php in vendor/guzzlehttp/guzzle/src/Handler/MockHandler.php

NotPromiseInstance.php in vendor/guzzlehttp/promises/tests/NotPromiseInstance.php

PrepareBodyMiddleware.php in vendor/guzzlehttp/guzzle/src/PrepareBodyMiddleware.php

RedirectMiddleware.php in vendor/guzzlehttp/guzzle/src/RedirectMiddleware.php

RequestException.php in vendor/guzzlehttp/guzzle/src/Exception/RequestException.php

RetryMiddleware.php in vendor/guzzlehttp/guzzle/src/RetryMiddleware.php

StreamHandler.php in vendor/guzzlehttp/guzzle/src/Handler/StreamHandler.php