Fix "Session" is not a known member of module

Note that "os" module is not used in Client.py.

Signed-off-by: Jun-Fei Cherng <jfcherng@realtek.com>

Author: jfcherng

blackduck/Client.py

@@ -11,7 +11,7 @@
 from .Authentication import BearerAuth
 import json
 import logging
-import os
+import requests
 from pprint import pformat
 import requests.packages.urllib3
 from requests.packages.urllib3.util.retry import Retry