How to execute Openstack CLIs using python subprocess.Popen (,,,env parameter)

Question

I have one function run_cmd using

p = subprocess.Popen( cmd, shell = True, stdout = subprocess.PIPE, stderr = subprocess.PIPE, cwd = scriptdir, env = myenv )

when I call run_cmd from main

run_cmd(cli,"on", haltOnError="on")

I don't know how to use env - myenv parameter from subprocess.Popen. As you are all know that, to run openstack CLI we must source to keystone_rc file where OS_ENV is from here.

export OS_USERNAME=admin
export OS_TENANT_NAME=admin
export NOVA_VERSION=1.1
export OS_PROJECT_NAME=admin
export OS_PASSWORD=xxxx_yyyy
export COMPUTE_API_VERSION=1.1
export no_proxy=,10.xxx.xxx.164,172.31.255.9
export OS_CLOUDNAME=overcloud
export OS_AUTH_URL=https://10.xxx.xxx.164:13000/v2.0

I have an alternate way to overcome my problem but I have to inject "source keystone_rc; openstack server list". If I can use env parameter from subprocess, that would be great. Any idea, I appreciate!.