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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def rm_crypttab(name, config='/etc/crypttab'):
    '''
    Remove the named mapping from the crypttab. If the described entry does not
    exist, nothing is changed, but the command succeeds by returning
    ``'absent'``. If a line is removed, it returns ``'change'``.

    CLI Example:

    .. code-block:: bash

        salt '*' cryptdev.rm_crypttab foo
    '''
    modified = False
    criteria = _crypttab_entry(name=name)

    # For each line in the config that does not match the criteria, add it to
    # the list. At the end, re-create the config from just those lines.
    lines = []
    try:
        with salt.utils.files.fopen(config, 'r') as ifile:
            for line in ifile:
                line = salt.utils.stringutils.to_unicode(line)
                try:
                    if criteria.match(line):
                        modified = True
                    else:
                        lines.append(line)

                except _crypttab_entry.ParseError:
                    lines.append(line)

    except (IOError, OSError) as exc:
        msg = 'Could not read from {0}: {1}'
        raise CommandExecutionError(msg.format(config, exc))

    if modified:
        try:
            with salt.utils.files.fopen(config, 'w+') as ofile:
                ofile.writelines((salt.utils.stringutils.to_str(line) for line in lines))
        except (IOError, OSError) as exc:
            msg = 'Could not write to {0}: {1}'
            raise CommandExecutionError(msg.format(config, exc))

    # If we reach this point, the changes were successful
    return 'change' if modified else 'absent'