'Return a list of stevedore extensions.
The returned stevedore extensions wrap the pollster object instances
returned by build_pollsters.'

@classmethod
def get_pollsters_extensions(cls, conf):

    extensions = []
    try:
        for (name, pollster) in cls.build_pollsters(conf):
            ext = extension.Extension(name, None, cls, pollster)
            extensions.append(ext)
    except Exception as err:
        raise ExtensionLoadError(err)
    return extensions
