Ensure valid partition boundaries are supplied.

def _validate_partition_boundary(boundary):
    '''
    Ensure valid partition boundaries are supplied.
    '''
    boundary = six.text_type(boundary)
    match = re.search(r'^([\d.]+)(\D*)$', boundary)
    if match:
        unit = match.group(2)
        if not unit or unit in VALID_UNITS:
            return
    raise CommandExecutionError(
        'Invalid partition boundary passed: "{0}"'.format(boundary)
    )