Revise paste apt-clone-clone.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from __future__ import (
    absolute_import, division, print_function, unicode_literals
)
from nine import (
    IS_PYTHON2, basestring, chr, class_types, filter, integer_types,
    implements_iterator, implements_to_string, implements_repr,
    input, iterkeys, iteritems, itervalues, long, map,
    native_str, nine, nimport, range, range_list, reraise, str, zip
)

argparse = nimport('argparse')
glob = nimport('glob')
grp = nimport('grp')
os = nimport('os')
pwd = nimport('pwd')
subprocess = nimport('subprocess')
sys = nimport('sys')
time = nimport('time')

DEFAULT_PREFIX = 'home_'

def run():
    """Runs this program.

The program runs 'apt-clone clone' to store the current package list
    into a time-stamped file in the given destination directory.

Returns:
        None
    """
    start_time = time.time()
    options = parse_cmd_line(default_prefix=DEFAULT_PREFIX)
    remove_old_files(
        pattern='{destdir}{sep}{prefix}*'.format(
            destdir=options['destdir'],
            sep=os.sep,
            prefix=options['prefix']),
        remove=options['remove'],
        verbose=options['verbose'])
    dest_prefix = generate_results_file_prefix(
        dest_dir=options['destdir'],
        prefix=options['prefix'])
    apt_clone_clone(
        dest_prefix=dest_prefix,
        verbose=options['verbose'])
    change_file_owner_group(
        pattern='{}*apt-clone*'.format(dest_prefix),
        user=options['user'],
        group=options['user'],
        verbose=options['verbose'])
    if options['verbose']:
        print('Done, in {} seconds!'.format(time.time() - start_time))

def parse_cmd_line(default_prefix):
    """Parses the command-line arguments.

Arguments:
        default_prefix: the default prefix for current package list

Returns:
        A dictionary with each of the supplied command-line arguments.
    """
    parser = argparse.ArgumentParser(
        description="Stores apt-clone clone results")
    parser.add_argument(
        'user',
        help=' '.join([
            'specify the name of the owner of the apt-clone clone results file;',
            'the results files user and group will be set to this value']))
    parser.add_argument(
        'destdir',
        help=' '.join([
            'specify the directory that the new results file',
            'will be saved into']))
    parser.add_argument(
        '--prefix', '-p',
        default=default_prefix,
        help=' '.join([
            'specify the prefix to use for the newly created results file',
            "(default: '%(default)s')"]))
    parser.add_argument(
        '--remove', '-r',
        action='store_true',
        default=False,
        help='specify this to have obsolete results files removed')
    parser.add_argument(
        '--verbose', '-v',
        action='store_true',
        default=False,
        help='specify this to display verbose output')
    # vars() turns Namespace into a regular dictionary
    options = vars(parser.parse_args())
    options['destdir'] = chomp_sep(options['destdir'])
    return options

def chomp_sep(dir_name):
    """Removes any trailing directory separator characters from the given
    directory name.

Arguments:
        dir_name: the name that has to have any trailing slashes removed

Returns:
        The directory name with no trailing separator characters
    """
    while dir_name.endswith(os.sep):
        dir_name = dir_name[:-1]
    return dir_name

def generate_results_file_prefix(dest_dir, prefix):
    """Generates a results file filename prefix.

Arguments:
        dest_dir: where the results file should be saved
        prefix: the prefix to use for the results file

Returns:
        A results file filename prefix of the form:
            <dest_dir>/<prefix><year><month><day><hour><minute><second>
        where the year, month, day, etc. values represent the local time
    """
    localtime = time.localtime()
    return ('{dest_dir}{sep}{prefix}{year:04d}{month:02d}{day:02d}' +
        '{hour:02d}{minute:02d}{second:02d}').format(
            dest_dir=dest_dir,
            prefix=prefix,
            year=localtime[0],
            month=localtime[1],
            day=localtime[2],
            hour=localtime[3],
            minute=localtime[4],
            second=localtime[5],
            sep=os.sep)

def remove_old_files(**kwargs):
    """Only keeps the newest files that match a glob pattern.

Arguments:
        kwargs: a dictionary with the following keys:-
            'pattern'   - the glob pattern of files to remove
            'remove'    - whether to remove old files
            'verbose'   - whether to output text describing non-fatal events

Returns:
        None
    """
    pattern = kwargs.pop('pattern')
    remove = kwargs.pop('remove')
    verbose= kwargs.pop('verbose')
    if kwargs:
        raise TypeError('Unexpected **kwargs: %r' % kwargs)
    if not remove:
        return
    for f in glob.glob(pattern):
        os.remove(f)
        if verbose:
            print("Removed file '{filename}'".format(filename=f))

def apt_clone_clone(dest_prefix, verbose):
    """Creates a clone file

Arguments:
        dest_prefix:    the prefix to use for the apt-clone clone results file
        verbose:        whether to output text describing non-fatal events

Returns:
        None
   """
    subprocess.call(
        'apt-clone clone "{}" &>/dev/null'.format(dest_prefix),
        shell=True)
    if verbose:
        print('Performed apt-clone clone to: {}'.format(dest_prefix))

def change_file_owner_group(**kwargs):
    """Changes the owner and group of the named file.

Arguments:
        kwargs: a dictionary with the following keys:-
            'pattern':  the glob pattern of files to change ownership of
            'user':     the new owner to assign to the file
            'group':    the new group to assign to the file;
                        this is the same as 'user' if not given
            'verbose':  whether to output text describing non-fatal events

Returns:
        None
    """
    pattern = kwargs.pop('pattern')
    user = kwargs.pop('user')
    group = kwargs.pop('group', user)
    verbose= kwargs.pop('verbose')
    if kwargs:
        raise TypeError('Unexpected **kwargs: %r' % kwargs)
    for filename in glob.glob(pattern):
        try:
            os.chown(filename,
                     pwd.getpwnam(user).pw_uid,
                     grp.getgrnam(group).gr_gid)
            if verbose:
                print(
                    ' '.join(
                        "Changed ownership of '{filename}'",
                        "'{user}:{group}'".format(
                            filename=filename,
                            user=user,
                            group=group)))
        except os.OSError as err:
            print("Unable to change ownership of "
                + "'{filename}' to '{user}:{group}' => {err}".format(
                    filename=filename,
                    user=user,
                    group=group,
                    err=err),
                file=sys.stderr)

if __name__ == '__main__':
    run()