**Problem**
* While adding e2e tests for AssumeRole functionality, it was noticed that some of the static credential e2e tests were flaky.
* The tests would sometimes fail with an AuthFailure.
**Solution**
* It was discovered that this error happened sometimes after a static credential rotation and that AuthFailure occurs if EC2 is invoked with the wrong credentials.
* Due to IAM's eventual consistency model, it can take some time (up to several seconds) for changes, including rotated credentials, to get propagated to all AWS services, including EC2.
* The tests were intermittently failing because sometimes the credentials would be propagated in time before invoking EC2 and other times they were not propagated in time.
* The fix is to add a retry mechanism when calling DescribeInstances. A 30 second window is defined in which the retries can take place.
* The retries happen only for AuthFailures. Any other failure will not trigger a retry.
**Testing**
* After making this change, the intermittent failures were no longer seen for the e2e tests
* The e2e tests cover updating/creating catalogs and sets as well us updating the host list. All pass.
* New unit tests were added to test the retry mechanism. Support had to be added to mock a series of DescribeInstances calls vs a single call
* New and existing unit tests passed
Matt Romanelli
f81151b58c