Get AWS VPC tags external data source when you need to assume a role.

vpc_tags_role.py

import json
import boto3
import sys

input_json = sys.stdin.read()
try:
    data = json.loads(input_json)
except ValueError as value_error:
    sys.exit(value_error)

boto_sts=boto3.client('sts')
stsresponse = boto_sts.assume_role(
    RoleArn=data["role_arn"],
    RoleSessionName='newsession'
)

newsession_id = stsresponse["Credentials"]["AccessKeyId"]
newsession_key = stsresponse["Credentials"]["SecretAccessKey"]
newsession_token = stsresponse["Credentials"]["SessionToken"]

ec2 = boto3.resource('ec2',
    region_name=data["region"],
    aws_access_key_id=newsession_id,
    aws_secret_access_key=newsession_key,
    aws_session_token=newsession_token
)
client = boto3.client('ec2',
    region_name=data["region"],
    aws_access_key_id=newsession_id,
    aws_secret_access_key=newsession_key,
    aws_session_token=newsession_token
)

filters = [{'Name':'tag:Name', 'Values':[data["vpc_name"]]}]
vpcs = list(ec2.vpcs.filter(Filters=filters))

tags = {}

for vpc in vpcs:
    response = client.describe_vpcs(
            VpcIds=[
                vpc.id,
            ]
    )
    for tag in response["Vpcs"][0]["Tags"]:
        tags[tag["Key"]] = tag["Value"]

sys.stdout.write(json.dumps(tags))