rc_extras[k]

    except KeyError, e:

        raise Exception('Missing key %s in os.environ %s' % (e, rc_extras))

    return AttributeDict(rc_extras)

def _set_extras(extras):

    os.environ['RC_SCM_DATA'] = json.dumps(extras)

def unique_id(hexlen=32):

    alphabet = "23456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghjklmnpqrstuvwxyz"

    return suuid(truncate_to=hexlen, alphabet=alphabet)

def suuid(url=None, truncate_to=22, alphabet=None):

    """

    Generate and return a short URL safe UUID.

    If the url parameter is provided, set the namespace to the provided

    URL and generate a UUID.

    :param url to get the uuid for

    :truncate_to: truncate the basic 22 UUID to shorter version

    The IDs won't be universally unique any longer, but the probability of

    a collision will still be very low.

    """

    # Define our alphabet.

    _ALPHABET = alphabet or "23456789ABCDEFGHJKLMNPQRSTUVWXYZ"

    # If no URL is given, generate a random UUID.

    if url is None:

        unique_id = uuid.uuid4().int

    else:

        unique_id = uuid.uuid3(uuid.NAMESPACE_URL, url).int

    alphabet_length = len(_ALPHABET)

    output = []

    while unique_id > 0:

        digit = unique_id % alphabet_length

        output.append(_ALPHABET[digit])

        unique_id = int(unique_id / alphabet_length)

    return "".join(output)[:truncate_to]

def get_current_rhodecode_user():

    """

    defined, else returns None.

    """

    from pylons import tmpl_context

    if hasattr(tmpl_context, 'rhodecode_user'):

        return tmpl_context.rhodecode_user

    return None