Remove downgrades from migrations

According to cross project spec
I622f89fe63327d44f9b229d3bd9e76e15acbaa7a downgrade
migrations should be removed.

Change-Id: Iee38d8ba5e414e67033db35db52724d3f9f84fd7

ironic_inspector/dbsync.py

@@ -39,7 +39,7 @@ def add_command_parsers(subparsers):
         parser = add_alembic_command(subparsers, name)
         parser.set_defaults(func=do_alembic_command)
 
-    for name in ['downgrade', 'stamp', 'show', 'edit']:
+    for name in ['stamp', 'show', 'edit']:
         parser = add_alembic_command(subparsers, name)
         parser.set_defaults(func=with_revision)
         parser.add_argument('--revision', nargs='?', required=True)

ironic_inspector/migrations/script.py.mako

@@ -30,7 +30,3 @@ ${imports if imports else ""}
 
 def upgrade():
     ${upgrades if upgrades else "pass"}
-
-
-def downgrade():
-    ${downgrades if downgrades else "pass"}

ironic_inspector/migrations/versions/578f84f38d_inital_db_schema.py

@@ -61,9 +61,3 @@ def upgrade():
         mysql_ENGINE='InnoDB',
         mysql_DEFAULT_CHARSET='UTF8'
     )
-
-
-def downgrade():
-    op.drop_table('nodes')
-    op.drop_table('attributes')
-    op.drop_table('options')

ironic_inspector/migrations/versions/d588418040d_add_rules.py

@@ -62,9 +62,3 @@ def upgrade():
         mysql_ENGINE='InnoDB',
         mysql_DEFAULT_CHARSET='UTF8'
     )
-
-
-def downgrade():
-    op.drop_table('rules')
-    op.drop_table('rule_conditions')
-    op.drop_table('rule_actions')

ironic_inspector/migrations/versions/e169a4a81d88_add_invert_field_to_rule_condition.py

@@ -31,7 +31,3 @@ import sqlalchemy as sa
 def upgrade():
     op.add_column('rule_conditions', sa.Column('invert', sa.Boolean(),
                                                nullable=True, default=False))
-
-
-def downgrade():
-    op.drop_column('rule_conditions', 'invert')

releasenotes/notes/no-downgrade-migrations-514bf872d9f944ed.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - Database migrations downgrade was removed. More info about
+    database migration/rollback could be found here
+    http://docs.openstack.org/openstack-ops/content/ops_upgrades-roll-back.html