DRIVERS-1396 introduced a retryable writes spec test that adds an error label to a write concern error and exposes the error to the test runner (since times:2 overcomes the first retry attempt). This resulted in a PHPLIB test failure because error labels within writeConcernErrors of libmongoc's bulk write reply are never collected by phongo_exception_add_error_labels.

libmongoc may be unique among drivers in that it reports all write concern errors in an array (CDRIVER-710) instead of a consolidated writeConcernError field described in the CRUD spec. This is a separate issue related to DRIVERS-1396.