Display progression on slow migration

src/documents/migrations/0014_auto_20180502_0852.py

@@ -7,7 +7,13 @@ from documents.models import DocumentType
 def transcription_to_document(apps, schema_editor):
     Document = apps.get_model('documents', 'Document')
     Transcription = apps.get_model('documents', 'Transcription')
-    for ts in Transcription.objects.all():
+    nb = Transcription.objects.all().count()
+    last = 0
+    for i,ts in enumerate(Transcription.objects.all()):
+        percent = int(100.0 * (i+1) / nb)
+        if percent % 5 == 0 and last != percent:
+            print(' > {}% => {} / {}'.format(percent, i, nb))
+            last = percent
         new_ts = Transcription(line=ts.line, score=ts.score, text=ts.text)
         new_ts.document_ptr = Document.objects.create(type=DocumentType.Transcription, name="Transcription '{}'".format(ts.text))
         new_ts.save()