'Create an authenticated client context.'

def _authenticate(self):

    self.pyrax = pyrax.create_context('rackspace')
    self.pyrax.auth_endpoint = self.context.auth_url
    LOG.info('Authenticating    username:    %s', self.context.username)
    tenant = self.context.tenant_id
    tenant_name = self.context.tenant
    self.pyrax.auth_with_token(self.context.auth_token, tenant_id=tenant, tenant_name=tenant_name)
    if (not self.pyrax.authenticated):
        LOG.warning('Pyrax    Authentication    Failed.')
        raise exception.AuthorizationFailure()
    LOG.info('User    %s    authenticated    successfully.', self.context.username)
