Creates a diagram of all the models for yacms and the given
    package name, generates a smaller version and add it to the
    docs directory for use in model-graph.rst

def build_modelgraph(docs_path, package_name="yacms"):
    """
    Creates a diagram of all the models for yacms and the given
    package name, generates a smaller version and add it to the
    docs directory for use in model-graph.rst
    """
    to_path = os.path.join(docs_path, "img", "graph.png")
    build_path = os.path.join(docs_path, "build", "_images")
    resized_path = os.path.join(os.path.dirname(to_path), "graph-small.png")
    settings = import_dotted_path(package_name +
                                  ".project_template.project_name.settings")
    apps = [a.rsplit(".")[1] for a in settings.INSTALLED_APPS
            if a.startswith("yacms.") or a.startswith(package_name + ".")]
    try:
        from django_extensions.management.commands import graph_models
    except ImportError:
        warn("Couldn't build model_graph, django_extensions not installed")
    else:
        options = {"inheritance": True, "outputfile": "graph.png",
                   "layout": "dot"}
        try:
            graph_models.Command().execute(*apps, **options)
        except Exception as e:
            warn("Couldn't build model_graph, graph_models failed on: %s" % e)
        else:
            try:
                move("graph.png", to_path)
            except OSError as e:
                warn("Couldn't build model_graph, move failed on: %s" % e)
    # docs/img/graph.png should exist in the repo - move it to the build path.
    try:
        if not os.path.exists(build_path):
            os.makedirs(build_path)
        copyfile(to_path, os.path.join(build_path, "graph.png"))
    except OSError as e:
        warn("Couldn't build model_graph, copy to build failed on: %s" % e)
    try:
        from PIL import Image
        image = Image.open(to_path)
        image.width = 800
        image.height = image.size[1] * 800 // image.size[0]
        image.save(resized_path, "PNG", quality=100)
    except Exception as e:
        warn("Couldn't build model_graph, resize failed on: %s" % e)
        return
    # Copy the dashboard screenshot to the build dir too. This doesn't
    # really belong anywhere, so we do it here since this is the only
    # spot we deal with doc images.
    d = "dashboard.png"
    copyfile(os.path.join(docs_path, "img", d), os.path.join(build_path, d))