Make auth plugins dest save to os_

If the auth plugin saves into the normal namespace like .user_id and
user_id is an argument of the command then the two argument collide with
each other.

This is fairly common, particularly in keystoneclient's shell.

There is a little bit of a compatibility concern in that the variables
on the returned namespace have changed, however the usage of this
function should be if you use register_argparse_arguments you should
also use load_from_argparse_arguments and that is not changed.

Change-Id: Id1cb0983a1e78661492acd78ad9aa67ff8d49250

keystoneclient/auth/base.py

@@ -151,7 +151,7 @@ class BaseAuthPlugin(object):
                                 default=default,
                                 metavar=opt.metavar,
                                 help=opt.help,
-                                dest=opt.dest)
+                                dest='os_%s' % opt.dest)
 
     @classmethod
     def load_from_argparse_arguments(cls, namespace, **kwargs):
@@ -165,7 +165,7 @@ class BaseAuthPlugin(object):
         :returns: An auth plugin, or None if a name is not provided.
         """
         for opt in cls.get_options():
-            val = getattr(namespace, opt.dest)
+            val = getattr(namespace, 'os_%s' % opt.dest)
             if val is not None:
                 val = opt.type(val)
             kwargs.setdefault(opt.dest, val)

keystoneclient/tests/auth/test_cli.py

@@ -62,6 +62,11 @@ class CliTests(utils.TestCase):
         a = cli.load_from_argparse_arguments(opts)
         self.assertTestVals(a)
 
+        self.assertEqual(name, opts.os_auth_plugin)
+        self.assertEqual(str(self.a_int), opts.os_a_int)
+        self.assertEqual(str(self.a_float), opts.os_a_float)
+        self.assertEqual(str(self.a_bool), opts.os_a_bool)
+
     @utils.mock_plugin
     def test_default_options(self, m):
         name = uuid.uuid4().hex