The ProjectBuild object is missing the project_id attribute that it uses when it makes the call to the gitlab API

Traceback (most recent call last):
File "gitlabtest.py", line 115, in
build.artifacts(streamed=True, action=saver)
File "{SCRUB}/python-gitlab/gitlab/objects.py", line 927, in artifacts
url = '/projects/%s/builds/%s/artifacts' % (self.project_id, self.id)
AttributeError: 'ProjectBuild' object has no attribute 'project_id'