Travis CI jobs fail with TypeError: attrib() got an unexpected keyword argument 'converter'

[kihneman]

The full traceback is:

Traceback (most recent call last):
  File "/home/travis/virtualenv/python2.7.14/lib/python2.7/site-packages/haas/plugins/discoverer.py", line 34, in test_error
    raise ImportError(message)
ImportError: Unable to import module u'okonomiyaki.runtimes.tests.test_runtime'
Traceback (most recent call last):
  File "/home/travis/virtualenv/python2.7.14/lib/python2.7/site-packages/haas/plugins/discoverer.py", line 368, in _load_from_file
    module = get_module_by_name(module_name)
  File "/home/travis/virtualenv/python2.7.14/lib/python2.7/site-packages/haas/utils.py", line 48, in get_module_by_name
    __import__(name)
  File "/home/travis/build/enthought/okonomiyaki/okonomiyaki/runtimes/__init__.py", line 2, in <module>
    from .runtime_metadata import IRuntimeMetadata, is_runtime_path_valid
  File "/home/travis/build/enthought/okonomiyaki/okonomiyaki/runtimes/runtime_metadata.py", line 7, in <module>
    import jsonschema
  File "/home/travis/virtualenv/python2.7.14/lib/python2.7/site-packages/jsonschema/__init__.py", line 22, in <module>
    from jsonschema._types import TypeChecker
  File "/home/travis/virtualenv/python2.7.14/lib/python2.7/site-packages/jsonschema/_types.py", line 49, in <module>
    class TypeChecker(object):
  File "/home/travis/virtualenv/python2.7.14/lib/python2.7/site-packages/jsonschema/_types.py", line 64, in TypeChecker
    _type_checkers = attr.ib(default=pmap(), converter=pmap)
TypeError: attrib() got an unexpected keyword argument 'converter'

I think this error is the same as python-jsonschema/jsonschema#449