require -> `pip install polib`

find_leftover_po.py

#! /usr/bin/env python
# -*- coding: utf-8 -*-
from __future__ import (print_function, division, absolute_import, unicode_literals, )


import polib
from polib import POEntry


def __eq__(self, other):
    return self.msgid == other.msgid and self.msgstr == other.msgstr
POEntry.__eq__ = __eq__


try:
    with open('ignored_id.txt', 'r') as f:
        IGNORERABLE_PO = set(l.rstrip() for l in f.readlines())
except IOError:
    IGNORERABLE_PO = []


def compare_po(x, y, strict=False):
    '''
    :param str x: filename to compare
    :param str y: filename to compare
    :param bool strict: If strict is True, error occurs when msgid is uneven.
    '''
    x_po = polib.pofile(x)
    y_po = list(polib.pofile(y))  # cannot use `set`
    if strict:
        x_ids, y_ids = set([_x.msgid for _x in x_po]), set([_y.msgid for _y in y_po])
        if not x_ids == y_ids:
            raise NoMatchedIdError(x_ids ^ y_ids)

    for x_l in x_po:
        if x_l in y_po and x_l.msgid not in IGNORERABLE_PO:
            yield x_l


class NoMatchedIdError(Exception):
    def __init__(self, missing_ids):
        self.missing_ids = missing_ids
        super(NoMatchedIdError, self).__init__('msgid is delete or modified!')


if __name__ == '__main__':
    import sys
    reload(sys)
    sys.setdefaultencoding('utf-8')
    desc = """
Usage: (this cmd) org_file_path modified_file_path

If you want to assign id is have to ignore, put `ignored_id.txt` and write in msgid.
"""
    # オプション増やす予定もないのでoptparserは使わない
    if sys.argv[1] in ('-h', '--help'):
        print(desc)
        sys.exit(0)

    x = sys.argv[1]
    y = sys.argv[2]
    output_format = 'id: {0}\nmsgstr: {1}\n'
    try:
        [print(output_format.format(z.msgid, z.msgstr)) for z in compare_po(x, y, strict=True)]
    except NoMatchedIdError as e:
        print(e)
        print('id are:\n' + '\n'.join(e.missing_ids))

tests.py

#! /usr/bin/env python
# -*- coding: utf-8 -*-
from __future__ import (print_function, division, absolute_import, unicode_literals, )

import sys
sys.path.append('../')
import find_leftover_po  # モンキーパッチを当てているのでこちらを先にimportする


import unittest
from os import path

import polib
from nose.tools import ok_, raises


suite = unittest.TestSuite()
loader = unittest.TestLoader()


def test_patch_applied():
    entry1 = polib.POEntry(msgid='id1', msgstr='str1')
    entry1a = polib.POEntry(msgid='id1', msgstr='str1')
    entry2 = polib.POEntry(msgid='id2', msgstr='str2')
    ok_(entry1 == entry1a)
    ok_(entry1 != entry2)


def test_find_leftover(use_strict=False):
    org = path.abspath(path.join(path.dirname(__file__), 'd3web.po'))
    changed = path.abspath(path.join(path.dirname(__file__), 'tes.po'))
    results = list(find_leftover_po.compare_po(org, changed, use_strict))
    unchanged_ids = [r.msgid for r in results]
    ok_(' is Failed' not in unchanged_ids)
    ok_('16bit unsigned integer type' not in unchanged_ids)


@raises(find_leftover_po.NoMatchedIdError)
def test_id_missing_error():
    test_find_leftover(use_strict=True)