Sync latest db and importutils from oslo

Changes include:

  7c0e25a Use importutils.try_import() for MySQLdb
  33b12d3 Implement importutils.try_import.
  cf705c5 Make project pyflakes clean.

Change-Id: I448f5208919d06ca0af54d2057b8f5e042862cd6

2 files changed, 13 insertions, 7 deletions

diff --git a/nova/openstack/common/db/sqlalchemy/session.py b/nova/openstack/common/db/sqlalchemy/session.py
index 2125b006d..bc889fc36 100644
--- a/nova/openstack/common/db/sqlalchemy/session.py
+++ b/nova/openstack/common/db/sqlalchemy/session.py
@@ -246,12 +246,6 @@ import time
 
 from eventlet import db_pool
 from eventlet import greenthread
-try:
-    import MySQLdb
-    from MySQLdb.constants import CLIENT as mysql_client_constants
-except ImportError:
-    MySQLdb = None
-    mysql_client_constants = None
 from sqlalchemy.exc import DisconnectionError, OperationalError, IntegrityError
 import sqlalchemy.interfaces
 import sqlalchemy.orm
@@ -259,10 +253,14 @@ from sqlalchemy.pool import NullPool, StaticPool
 from sqlalchemy.sql.expression import literal_column
 
 from nova.openstack.common import cfg
+from nova.openstack.common import importutils
 from nova.openstack.common import log as logging
 from nova.openstack.common.gettextutils import _
 from nova.openstack.common import timeutils
 
+MySQLdb = importutils.try_import('MySQLdb')
+if MySQLdb is not None:
+    from MySQLdb.constants import CLIENT as mysql_client_constants
 
 sql_opts = [
     cfg.StrOpt('sql_connection',
diff --git a/nova/openstack/common/importutils.py b/nova/openstack/common/importutils.py
index f45372b4d..9dec764fb 100644
--- a/nova/openstack/common/importutils.py
+++ b/nova/openstack/common/importutils.py
@@ -29,7 +29,7 @@ def import_class(import_str):
     try:
         __import__(mod_str)
         return getattr(sys.modules[mod_str], class_str)
-    except (ValueError, AttributeError), exc:
+    except (ValueError, AttributeError):
         raise ImportError('Class %s cannot be found (%s)' %
                           (class_str,
                            traceback.format_exception(*sys.exc_info())))
@@ -57,3 +57,11 @@ def import_module(import_str):
     """Import a module."""
     __import__(import_str)
     return sys.modules[import_str]
+
+
+def try_import(import_str, default=None):
+    """Try to import a module and if it fails return default."""
+    try:
+        return import_module(import_str)
+    except ImportError:
+        return default