Add importutils

They will be used when importing versioned modules.

openstack-common.conf

@@ -1,6 +1,7 @@
 [DEFAULT]
 
 # The list of modules to copy from openstack-common
+module=importutils
 
 # The base module to hold the copy of openstack.common
 base=tuskarclient

tuskarclient/openstack/common/importutils.py

@@ -0,0 +1,68 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2011 OpenStack Foundation.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+"""
+Import related utilities and helper functions.
+"""
+
+import sys
+import traceback
+
+
+def import_class(import_str):
+    """Returns a class from a string including module and class."""
+    mod_str, _sep, class_str = import_str.rpartition('.')
+    try:
+        __import__(mod_str)
+        return getattr(sys.modules[mod_str], class_str)
+    except (ValueError, AttributeError):
+        raise ImportError('Class %s cannot be found (%s)' %
+                          (class_str,
+                           traceback.format_exception(*sys.exc_info())))
+
+
+def import_object(import_str, *args, **kwargs):
+    """Import a class and return an instance of it."""
+    return import_class(import_str)(*args, **kwargs)
+
+
+def import_object_ns(name_space, import_str, *args, **kwargs):
+    """Tries to import object from default namespace.
+
+    Imports a class and return an instance of it, first by trying
+    to find the class in a default namespace, then failing back to
+    a full path if not found in the default namespace.
+    """
+    import_value = "%s.%s" % (name_space, import_str)
+    try:
+        return import_class(import_value)(*args, **kwargs)
+    except ImportError:
+        return import_class(import_str)(*args, **kwargs)
+
+
+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