marvin_refactor: exception handle for non-standard libraries

non-standard python libraries that are not installed by default on
python installations need to be exception handled appropriately

Signed-off-by: Prasanna Santhanam <tsp@apache.org>

tools/marvin/marvin/TestCaseExecuteEngine.py

@@ -15,7 +15,10 @@
 # specific language governing permissions and limitations
 # under the License.
 
-import unittest2 as unittest
+try:
+    import unittest2 as unittest
+except ImportError:
+    import unittest
 import os
 import sys
 import logging

tools/marvin/marvin/cloudstackConnection.py

@@ -15,7 +15,14 @@
 # specific language governing permissions and limitations
 # under the License.
 
-import requests
+try:
+    import requests
+    from requests import ConnectionError
+    from requests import HTTPError
+    from requests import Timeout
+    from requests import RequestException
+except ImportError:
+    raise Exception("requests installation not found. use pip install requests to continue")
 import urllib
 import base64
 import hmac
@@ -25,10 +32,6 @@ import time
 from marvin import cloudstackException
 from marvin.cloudstackAPI import *
 from marvin import jsonHelper
-from requests import ConnectionError
-from requests import HTTPError
-from requests import Timeout
-from requests import RequestException
 
 
 class CloudConnection(object):

tools/marvin/marvin/dbConnection.py

@@ -15,13 +15,14 @@
 # specific language governing permissions and limitations
 # under the License.
 
-import mysql
+try:
+    import mysql
+    from mysql import connector
+    from mysql.connector import errors
+except ImportError:
+    raise Exception("mysql-connector-python not installed. pip install mysql-connector-python to continue")
 import contextlib
-from mysql import connector
-from mysql.connector import errors
-from contextlib import closing
 import cloudstackException
-import sys
 import os
 
 

tools/marvin/marvin/remoteSSHClient.py

@@ -20,7 +20,6 @@ import time
 import cloudstackException
 import contextlib
 import logging
-from contextlib import closing
 
 
 class remoteSSHClient(object):

tools/marvin/marvin/util.py

@@ -19,7 +19,6 @@ from marvin.entity.template import Template
 from marvin.entity.zone import Zone
 from marvin.entity.serviceoffering import ServiceOffering
 from marvin.entity.domain import Domain
-from marvin.entity.guestos import GuestOS
 
 def get_domain(apiclient):
     "Returns a default `ROOT` domain"