Allow to fail instead of skip in DbFixture

Tests using DbFixture[1] are currently skipped if the database is
unavailable (no db service, no permissions, etc.) which is fine when
tests are runned by developers but not when runned by the gate jobs.

This change defines the attribute DbFixture.SKIP_ON_UNAVAILABLE_DB: when
the database is unvailable, tests are:

* skipped when SKIP_ON_UNAVAILABLE_DB=True (default, legacy behaviour),
* failed when SKIP_ON_UNAVAILABLE_DB=False.

[1] oslo.db.sqlalchemy.test_base

Change-Id: I067f46417fefe252c650e1e5e590e83547b11b6a
Closes-Bug: #1404093

oslo_db/sqlalchemy/test_base.py

@@ -49,9 +49,10 @@ class DbFixture(fixtures.Fixture):
     # are referring to them directly.
     DBNAME = PASSWORD = USERNAME = 'openstack_citest'
 
-    def __init__(self, test):
+    def __init__(self, test, skip_on_unavailable_db=True):
         super(DbFixture, self).__init__()
         self.test = test
+        self.skip_on_unavailable_db = skip_on_unavailable_db
 
     def setUp(self):
         super(DbFixture, self).setUp()
@@ -63,7 +64,11 @@ def setUp(self):
             self.test, self.test.resources, testresources._get_result()
         )
         if not hasattr(self.test, 'db'):
-            self.test.skip("database '%s' unavailable" % self.DRIVER)
+            msg = "database '%s' unavailable" % self.DRIVER
+            if self.skip_on_unavailable_db:
+                self.test.skip(msg)
+            else:
+                self.test.fail(msg)
 
         if self.test.SCHEMA_SCOPE:
             self.test.engine = self.test.transaction_engine
@@ -83,6 +88,7 @@ class DbTestCase(test_base.BaseTestCase):
 
     FIXTURE = DbFixture
     SCHEMA_SCOPE = None
+    SKIP_ON_UNAVAILABLE_DB = True
 
     _schema_resources = {}
     _database_resources = {}
@@ -144,7 +150,9 @@ def resources(self):
 
     def setUp(self):
         super(DbTestCase, self).setUp()
-        self.useFixture(self.FIXTURE(self))
+        self.useFixture(
+            self.FIXTURE(
+                self, skip_on_unavailable_db=self.SKIP_ON_UNAVAILABLE_DB))
 
     def generate_schema(self, engine):
         """Generate schema objects to be used within a test.