got 500 on running with -parallel-finish option in circleci

[hftsin]

The coveralls return 500 when goveralls is executed with -parallel-finish option. I describe the issue with a simplified example as follows.

jobs:
   coverage:
      - run: goveralls -parallel xxxxx
    coverage-finish:
      - run: goveralls -parallel-finish

workflows:
   coverage-workflow:
       jobs:
          - coverage:
                 name: coverage-foo
          - coverage:
                 name: coverage-bar      
          - coverage-finish:
             - requires:
                   - coverage-foo
                   - coverage-bar

Job coverage-foo and coverage-bar submit the coverage report concurrently, and the job coverage-finish marks the coverage submit as done once the former two jobs finish.

In CircleCI, the coverage-finish job fails with an response status code of 500 from coveralls.io server.