Print to stderr when keyring module is missing.

Updates keystoneclient so that it uses a print statement to
stderr instead of a logger.warn if stderr is a tty.
This works around problems caused by the fact that logging isn't always
initialized when this module import runs (and fails) thus causing:

  No handlers could be found for logger "keystoneclient.client"

instead of the intended log message.

Fixes LP Bug #1090396

Change-Id: I94e2c45eec14edfe3c2f356af6907aa827808a13

keystoneclient/client.py

@@ -10,6 +10,7 @@ OpenStack Client interface. Handles the REST calls and responses.
 
 import copy
 import logging
+import sys
 import urlparse
 
 import httplib2
@@ -38,7 +39,10 @@ try:
     import keyring
     import pickle
 except ImportError:
-    _logger.warning('Failed to load keyring modules.')
+    if (hasattr(sys.stderr, 'isatty') and sys.stderr.isatty()):
+        print >> sys.stderr, 'Failed to load keyring modules.'
+    else:
+        _logger.warning('Failed to load keyring modules.')
     keyring_available = False