Delete a project's avatar.

        :param project: ID or key of the project to delete the avatar from
        :param avatar: ID of the avatar to delete

def delete_project_avatar(self, project, avatar):
        """Delete a project's avatar.

        :param project: ID or key of the project to delete the avatar from
        :param avatar: ID of the avatar to delete
        """
        url = self._get_url('project/' + project + '/avatar/' + avatar)
        return self._session.delete(url)