Stress test is flaky with "exceeds block gas limit"

[LefterisJP]

As was seen in this PR the stress test seems to be failing in a flaky manner with ValueError: {'code': -32000, 'message': 'exceeds block gas limit'}�[0m

The complete log can be seen here

[LefterisJP]

Probably fixed by: #2516 as seen in #2521

[LefterisJP]

Not fixed yet. After #2441, due to the Travis changes, Travis is slower again and this occurs.