po_spliter.py

from babel.messages import catalog, pofile

SPLITS = 10

catalogs = [catalog.Catalog(locale='es_ES') for _ in range(0, SPLITS)]
with open('locales/es_ES/LC_MESSAGES/messages.po', 'r') as f:
    po = pofile.read_po(f)
untranslated = [s.id for s in po if not s.string]
for idx, string in enumerate(untranslated):
    c_idx = idx % SPLITS
    c = catalogs[c_idx]
    c.add(string)
for idx, c in enumerate(catalogs):
    with open('locales/es_ES/LC_MESSAGES/messages.{}.po'.format(idx), 'w') as f:
        pofile.write_po(f, c)