fix #283: don't import keyring unless needed.

Now we only import the keyring right where we use it.  This will be helpful on Linux servers that don't have keyrings.

Author: adobeDan

user_sync/config.py

@@ -25,7 +25,6 @@
 import subprocess
 import types
 
-import keyring
 import yaml
 import six
 
@@ -600,6 +599,7 @@ def get_credential(self, name, user_name, none_allowed=False):
             raise AssertionException('%s: cannot contain setting for both "%s" and "%s"' % (scope, name, keyring_name))
         if secure_value_key:
             try:
+                import keyring
                 value = keyring.get_password(service_name=secure_value_key, username=user_name)
             except Exception as e:
                 raise AssertionException('%s: Error accessing secure storage: %s' % (scope, e))