Fix deploy backward migrations (#2471)

Fixed backward migrations for feature/deployment branch

src/ralph/data_center/migrations/0014_custom_move_managment_to_networks.py

@@ -27,13 +27,15 @@ def move_to_networks(apps, schema_editor):
 
 
 def move_from_networks(apps, schema_editor):
-    DataCenterAsset = apps.get_model('data_center', 'DataCenterAsset')
     IPAddress = apps.get_model('networks', 'IPAddress')
-    ips = IPAddress.objects.exclude(is_management=False, base_object=None)
+    ips = IPAddress.objects.filter(
+        is_management=True, base_object__asset__datacenterasset__isnull=False
+    )
     for ip in ips:
-        ip.base_object.management_ip_old = ip.address
-        ip.base_object.management_hostname_old = ip.hostname
-        ip.base_object.save()
+        dca = ip.base_object.asset.datacenterasset
+        dca.management_ip_old = ip.address
+        dca.management_hostname_old = ip.hostname
+        dca.save()
 
 
 class Migration(migrations.Migration):

src/ralph/networks/migrations/0003_custom_link_ips_to_eth.py

@@ -20,7 +20,12 @@ def move_from_base_object_to_ethernet(apps, schema_editor):
 
 
 def move_from_ethernet_to_base_object(apps, schema_editor):
-    pass
+    Ethernet = apps.get_model('assets', 'Ethernet')
+    for eth in Ethernet.objects.filter(
+        ipaddress__isnull=False,
+    ):
+        eth.ipaddress.base_object_id = eth.base_object_id
+        eth.ipaddress.save()
 
 
 class Migration(migrations.Migration):

src/ralph/networks/models/networks.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import ipaddress
+import logging
 import socket
 import struct
 from itertools import chain
@@ -9,6 +10,7 @@
 from django.db import models, transaction
 from django.db.models import Q
 from django.db.models.signals import post_migrate
+from django.db.utils import ProgrammingError
 from django.dispatch import receiver
 from django.utils.functional import cached_property
 from django.utils.translation import ugettext_lazy as _
@@ -26,6 +28,8 @@
 from ralph.networks.fields import IPNetwork
 from ralph.networks.models.choices import IPAddressStatus
 
+logger = logging.getLogger(__name__)
+
 
 class NetworkKind(NamedMixin, models.Model):
     class Meta:
@@ -585,4 +589,9 @@ def rebuild_handler(sender, **kwargs):
     """
     # post_migrate is called after each app's migrations
     if sender.name == 'ralph.' + Network._meta.app_label:
-        Network.objects.rebuild()
+        try:
+            Network.objects.rebuild()
+        except ProgrammingError:
+            # this may happen during unapplying initial migration for networks
+            # app
+            logger.warning('ProgrammingError during Network rebuilding')