Merge ~alexsander-souza/maas:lp1966506_check_pg_version into maas:master

[Alexsander de Souza]

Check pg version before applying migrations

Some migrations may fail on earlier versions of postgres, leaving the system in a broken state. This aborts the process before any change is made.

Fixes LP#1966506

[Christian Grabowski (cgrabowski)]

+1

review: Approve

[MAAS Lander (maas-lander)]

UNIT TESTS
-b lp1966506_check_pg_version lp:~alexsander-souza/maas/+git/maas into -b master lp:~maas-committers/maas

STATUS: SUCCESS
COMMIT: 2b70805907d0f7feec3d23d48ae939f7e6db05fc

review: Approve

diff --git a/src/maasserver/management/commands/dbupgrade.py b/src/maasserver/management/commands/dbupgrade.py
index 0d2bd5f..ddf5582 100644
--- a/src/maasserver/management/commands/dbupgrade.py
+++ b/src/maasserver/management/commands/dbupgrade.py
@@ -13,6 +13,8 @@ from django.core.management import call_command
 from django.core.management.base import BaseCommand
 from django.db import connections, DEFAULT_DB_ALIAS
 
+from maasserver.plugin import PGSQL_MIN_VERSION, UnsupportedDBException
+
 
 class Command(BaseCommand):
     help = "Upgrades database schema for MAAS regiond."
@@ -100,6 +102,13 @@ class Command(BaseCommand):
         database = options.get("database")
         no_triggers = options.get("no_triggers")
 
+        # Check database version
+        conn = connections[database]
+        conn.ensure_connection()
+        pg_ver = conn.cursor().connection.server_version
+        if pg_ver // 100 < PGSQL_MIN_VERSION:
+            raise UnsupportedDBException(pg_ver)
+
         # First, drop any views that may already exist. We don't want views
         # that that depend on a particular schema to prevent schema
         # changes due to the dependency. The views will be recreated at the