python3: Fix traceback while running tests

Fix:

TypeError: Unicode-objects must be encoded before hashing

while running tests. This is due to the fact in python3 hashlib.md5
works with bytes and we are passing unicode strings.

Change-Id: I27a57d6afb2412e11bc2802e4559d56c5b5592a9
Signed-off-by: Chuck Short <chuck.short@canonical.com>

novaclient/base.py

@@ -97,7 +97,8 @@ def completion_cache(self, cache_type, obj_class, mode):
         # pair
         username = utils.env('OS_USERNAME', 'NOVA_USERNAME')
         url = utils.env('OS_URL', 'NOVA_URL')
-        uniqifier = hashlib.md5(username + url).hexdigest()
+        uniqifier = hashlib.md5(username.encode('utf-8') +
+                                url.encode('utf-8')).hexdigest()
 
         cache_dir = os.path.expanduser(os.path.join(base_dir, uniqifier))