a script to convert your docker-compose.yml (version 2) with build node to image node; this script required DOCKERHUB_USER environment available.

build-tag-push.py

#!/usr/bin/python

import os
import subprocess
import time
import yaml
import re

user_name = os.environ.get("DOCKERHUB_USER")

if not user_name:
    print "Please set DOCKERHUB_USER to your user name.:"
    print "export DOCKERHUB_USER=zoe"
    exit(1)

print "DOCKERHUB_USER=%s" % user_name

# Get the name of the current directory
project_name = os.path.basename(os.path.realpath("."))

# Generate version number for built
version = str(int(time.time()))

input_file = os.environ.get("DOCKER_COMPOSE_YML", "docker-compose.yml")
output_file = os.environ.get("DOCKER_COMPOSE_YML", "docker-compose.yml-{}".format(version))

if input_file == output_file == "docker-compose.yml":
    print "I will not clobber your docker-compose.yml file."
    print "Please unset DOCKER_COMPOSE_YML or set it to something else."
    exit(1)

print "Input file: {}".format(input_file)
print "Output file: {}".format(output_file)

# Execute "docker-compose build" and abort if it fails.
subprocess.check_call(["docker-compose", "-f", input_file, "build"])

# Load the services from the input docker-compose.yml file.
stack = yaml.load(open(input_file))

# Modified the script so that it handle version 2 file.
if "services" not in stack:
    print "This script expect a `services` node in docker-compose.yml"
    exit(1)

services = stack["services"]

# Iterate over all services that have a "build" definition
# Tag them, and initiate a push in the background.
push_operations = dict()
for service_name, service in services.items():
    if "build" in service:
        compose_image = "{}_{}".format(project_name, service_name)
        hub_image = "{}/{}_{}:{}".format(user_name, project_name, service_name, version)
        # Re-tag the image so that it can be uploaded to the the Docker Hub.
        subprocess.check_call(["docker", "tag", compose_image, hub_image])
        # Spawn "docker push" to upload the image.
        push_operations[service_name] = subprocess.Popen(["docker", "push", hub_image])
        # Replace the "build" definition by an "image" definition,
        # using the name of the image on the Docker Hub.
        del service["build"]
        service["image"] = hub_image

# Wait for push operations to complete.
for service_name, popen_object in push_operations.items():
    print "Waiting for {} push to complete...".format(service_name)
    popen_object.wait()
    print "Done."

# Write the new docker-compose.yml file.
with open(output_file, "w") as f:
    yaml.safe_dump(stack, f, default_flow_style=False)

# yaml that is produced is a bit buggy.
fh = open(output_file, "r+")
lines = map(lambda a: re.sub(r"^\s{4}-", "      -", a), fh.readlines())
fh.close()
with open(output_file, "w") as f:
    f.writelines(lines)

print "Wrote new compose file."
print "COMPOSE_FILE={}".format(output_file)