Attept to create/update pages from JSON string json.  user is the
    user that will be used when creating a page if a page's original
    author can't be found.  preferred_lang is the language code of the
    slugs to include in error messages (defaults to
    settings.PAGE_DEFAULT_LANGUAGE).

    Returns (errors, pages_created) where errors is a list of strings
    and pages_created is a list of: (page object, created bool,
    messages list of strings) tuples.

    If any errors are detected there the error list will contain
    information for the user and no pages will be created/updated.

def json_to_pages(json, user, preferred_lang=None):
    """
    Attept to create/update pages from JSON string json.  user is the
    user that will be used when creating a page if a page's original
    author can't be found.  preferred_lang is the language code of the
    slugs to include in error messages (defaults to
    settings.PAGE_DEFAULT_LANGUAGE).

    Returns (errors, pages_created) where errors is a list of strings
    and pages_created is a list of: (page object, created bool,
    messages list of strings) tuples.

    If any errors are detected there the error list will contain
    information for the user and no pages will be created/updated.
    """
    from .models import Page
    if not preferred_lang:
        preferred_lang = settings.PAGE_DEFAULT_LANGUAGE

    d = simplejson.loads(json)
    try:
        errors = validate_pages_json_data(d, preferred_lang)
    except KeyError as e:
        errors = [_('JSON file is invalid: %s') % (e.args[0],)]

    pages_created = []
    if not errors:
        # pass one
        for p in d['pages']:
            pages_created.append(
                Page.objects.create_and_update_from_json_data(p, user))
        # pass two
        for p, results in zip(d['pages'], pages_created):
            page, created, messages = results
            rtcs = p['redirect_to_complete_slug']
            if rtcs:
                messages.extend(page.update_redirect_to_from_json(rtcs))
        # clean up MPTT links
        #Page.objects.rebuild()

    return errors, pages_created