def cmp_pkgrevno(package, revno, pkgcache=None):
    """Compare supplied revno with the revno of the installed package.

    *  1 => Installed revno is greater than supplied arg
    *  0 => Installed revno is the same as supplied arg
    * -1 => Installed revno is less than supplied arg

    This function imports apt_cache function from charmhelpers.fetch if
    the pkgcache argument is None. Be sure to add charmhelpers.fetch if
    you call this function, or pass an apt_pkg.Cache() instance.
    """
    import apt_pkg
    if not pkgcache:
        from charmhelpers.fetch import apt_cache
        pkgcache = apt_cache()
    pkg = pkgcache[package]
    return apt_pkg.version_compare(pkg.current_ver.ver_str, revno)
Compare supplied revno with the revno of the installed package.

    *  1 => Installed revno is greater than supplied arg
    *  0 => Installed revno is the same as supplied arg
    * -1 => Installed revno is less than supplied arg

    This function imports apt_cache function from charmhelpers.fetch if
    the pkgcache argument is None. Be sure to add charmhelpers.fetch if
    you call this function, or pass an apt_pkg.Cache() instance.