ed list of versions starting with default Python
    version (if available) then list of suppored versions greater than default
    one followed by reversed list of older versions.

    List of versions sorted this way can be used in Depends field.

    :param vrepr: return string represenatations of versions, by default the
        same format is used as in :param:`versions`

    >>> debsorted([(2, 6), (3, 1), (3, 2), (3, 3), (2, 7)])[0] == DEFAULT
    True
    >>> debsorted(('2.4', '3.2', '2.6', '2.7'))[-1]
    (2, 4)
    >>> debsorted(set([(2, 1), (2, 2)]))
    [(2, 2), (2, 1)]
    >>> debsorted([(2, 1), (2, 2)], return_str=True)
    ['2.2', '2.1']
    )	r`