Add data migrations to the sources app migraton 0019 to ensure all labels are unique before performing the schema migations.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

HISTORY.rst

@@ -1,3 +1,11 @@
+3.1.8 (2018-10-XX)
+==================
+* Reorganize documentation into topics and chapters.
+* Add Workflows and API chapters.
+* Add new material from the Wiki to the documentation.
+* Add data migrations to the sources app migraton 0019 to ensure all labels
+  are unique before performing the schema migations.
+
 3.1.7 (2018-10-14)
 ==================
 * Fix an issue with some browsers not firing the .load event on cached

mayan/apps/sources/migrations/0019_auto_20180803_0440.py

@@ -5,6 +5,28 @@ from __future__ import unicode_literals
 from django.db import migrations, models
 
 
+def make_labels_unique(apps, schema_editor):
+    Source = apps.get_model('sources', 'Source')
+
+    for source in Source.objects.using(schema_editor.connection.alias).all():
+        # Look for sources with the same label
+        duplicate_queryset = Source.objects.using(schema_editor.connection.alias).filter(label=source.label).exclude(pk=source.pk)
+        if duplicate_queryset:
+            # If a duplicate is found, append the id to the original source
+            # label
+            source.label = '{}__{}'.format(source.label, source.pk)
+            source.save()
+
+
+def make_labels_unique_reverse(apps, schema_editor):
+    Source = apps.get_model('sources', 'Source')
+
+    for source in Source.objects.using(schema_editor.connection.alias).all():
+        if source.label.endswith('__{}'.format(source.pk)):
+            source.label = source.label.replace('__{}'.format(source.pk), '')
+            source.save()
+
+
 class Migration(migrations.Migration):
 
     dependencies = [
@@ -12,6 +34,9 @@ class Migration(migrations.Migration):
     ]
 
     operations = [
+        migrations.RunPython(
+            make_labels_unique, reverse_code=make_labels_unique_reverse
+        ),
         migrations.AlterField(
             model_name='source',
             name='label',