'Return devices\' sizes in Mb'

def _get_devices_sizes(self, dev_paths):

    (out, _err) = self._execute('blockdev', '--getsize64', run_as_root=True, *dev_paths)
    dev_sizes = {}
    out = out.split('\n')
    for (n, size) in enumerate(out[:(-1)]):
        dev_sizes[dev_paths[n]] = (int(size) / units.Mi)
    return dev_sizes
