Hi, I try to code a Python script that can create/delete VM in my OpenStack cloud. Following the https://docs.openstack.org/mitaka/user-guide/sdk_compute_apis.html#list-servers-api-v2 (doc), I made this:

#!/usr/bin/env python

from os import environ
from novaclient.client import Client

def get_nova_credentials_v2():
    d = {}
    d['version'] = '2'
    d['username'] = environ['OS_USERNAME']
    d['password'] = environ['OS_PASSWORD']
    d['auth_url'] = environ['OS_AUTH_URL']
    d['project_id'] = environ['OS_TENANT_NAME']
    return d

credentials = get_nova_credentials_v2()
nova_client = Client(**credentials)

print(nova_client.servers.list())

Before running the code, i source the following openrc file that was created by DevStack:

#!/usr/bin/env bash
#
# source openrc [username] [projectname]
#
# Configure a set of credentials for $PROJECT/$USERNAME:
#   Set OS_PROJECT_NAME to override the default project 'demo'
#   Set OS_USERNAME to override the default user name 'demo'
#   Set ADMIN_PASSWORD to set the password for 'admin' and 'demo'

# NOTE: support for the old NOVA_* novaclient environment variables has
# been removed.

if [[ -n "$1" ]]; then
    OS_USERNAME=$1
fi
if [[ -n "$2" ]]; then
    OS_PROJECT_NAME=$2
fi

# Find the other rc files
RC_DIR=$(cd $(dirname "${BASH_SOURCE:-$0}") && pwd)

# Import common functions
source $RC_DIR/functions

# Load local configuration
source $RC_DIR/stackrc

# Load the last env variables if available
if [[ -r $RC_DIR/.stackenv ]]; then
    source $RC_DIR/.stackenv
fi

# Get some necessary configuration
source $RC_DIR/lib/tls

# The OpenStack ecosystem has standardized the term **project** as the
# entity that owns resources.  In some places **tenant** remains
# referenced, but in all cases this just means **project**.  We will
# warn if we need to turn on legacy **tenant** support to have a
# working environment.
export OS_PROJECT_NAME=${OS_PROJECT_NAME:-demo}

echo "WARNING: setting legacy OS_TENANT_NAME to support cli tools."
export OS_TENANT_NAME=$OS_PROJECT_NAME

# In addition to the owning entity (project), nova stores the entity performing
# the action as the **user**.
export OS_USERNAME=${OS_USERNAME:-demo}

# With Keystone you pass the keystone password instead of an api key.
# Recent versions of novaclient use OS_PASSWORD instead of NOVA_API_KEYs
# or NOVA_PASSWORD.
export OS_PASSWORD=${ADMIN_PASSWORD:-secret}

# Region
export OS_REGION_NAME=${REGION_NAME:-RegionOne}

# Set the host API endpoint. This will default to HOST_IP if SERVICE_IP_VERSION
# is 4, else HOST_IPV6 if it's 6. SERVICE_HOST may also be used to specify the
# endpoint, which is convenient for some localrc configurations. Additionally,
# some exercises call Glance directly. On a single-node installation, Glance
# should be listening on a local IP address, depending on the setting of
# SERVICE_IP_VERSION. If its running elsewhere, it can be set here.
if [[ $SERVICE_IP_VERSION == 6 ]]; then
    HOST_IPV6=${HOST_IPV6:-::1}
    SERVICE_HOST=${SERVICE_HOST:-[$HOST_IPV6]}
    GLANCE_HOST=${GLANCE_HOST:-[$HOST_IPV6]}
else
    HOST_IP=${HOST_IP:-127.0.0.1}
    SERVICE_HOST=${SERVICE_HOST:-$HOST_IP}
    GLANCE_HOST=${GLANCE_HOST:-$HOST_IP}
fi

# Identity API version
export OS_IDENTITY_API_VERSION=${IDENTITY_API_VERSION:-3}

# Ask keystoneauth1 to use keystone
export OS_AUTH_TYPE=password

# Authenticating against an OpenStack cloud using Keystone returns a **Token**
# and **Service Catalog**.  The catalog contains the endpoints for all services
# the user/project has access to - including nova, glance, keystone, swift, ...
# We currently recommend using the version 3 *identity api*.
#

# If you don't have a working .stackenv, this is the backup position
KEYSTONE_BACKUP=$SERVICE_PROTOCOL://$SERVICE_HOST:5000
KEYSTONE_AUTH_URI=${KEYSTONE_AUTH_URI:-$KEYSTONE_BACKUP}

export OS_AUTH_URL=${OS_AUTH_URL:-$KEYSTONE_AUTH_URI ...