Use CommandFailed exception from tempest_lib

Remove exceptions.py from functional/common.
Import exception with the same code from the tempest_lib to tests.

Change-Id: Ifaa658209c18dd608836079f57ed18fcf10fb84e

Author: kromanenko

functional/common/exceptions.py

@@ -18,7 +18,7 @@
 
 import six
 
-from functional.common import exceptions
+from tempest_lib import exceptions
 
 COMMON_DIR = os.path.dirname(os.path.abspath(__file__))
 FUNCTIONAL_DIR = os.path.normpath(os.path.join(COMMON_DIR, '..'))

functional/common/test.py

@@ -15,8 +15,8 @@
 
 import testtools
 
-from functional.common import exceptions
 from functional.common import test
+from tempest_lib import exceptions
 
 
 class ServerTests(test.TestCase):

functional/tests/compute/v2/test_server.py

@@ -11,8 +11,8 @@
 #    under the License.
 
 from tempest_lib.common.utils import data_utils
+from tempest_lib import exceptions
 
-from functional.common import exceptions
 from functional.tests.identity.v2 import test_identity
 
 

functional/tests/identity/v2/test_user.py

@@ -11,8 +11,8 @@
 #    under the License.
 
 from tempest_lib.common.utils import data_utils
+from tempest_lib import exceptions
 
-from functional.common import exceptions
 from functional.tests.identity.v3 import test_identity