Trivial: Fix coding style in examples in doc

Now, we use i18n strings for help and log messages,
and standardize the usage of logger. So fix those
in the example in doc.

Change-Id: Ibbc051b12133699811dd35a7e77a10de50ed8e44

Author: Tang Chen

doc/source/command-errors.rst

@@ -51,7 +51,7 @@ raised that includes the name of the file that was attempted to be opened.
                     ) as p:
                         public_key = p.read()
                 except IOError as e:
-                    msg = "Key file %s not found: %s"
+                    msg = _("Key file %s not found: %s")
                     raise exceptions.CommandError(
                         msg % (parsed_args.public_key, e),
                     )
@@ -135,7 +135,7 @@ remaining arguments are set using the ``update()`` method.
                     parsed_args.property,
                 )
             except SomeException:      # Need to define the exceptions to catch here
-                self.app.log.error("Property set failed")
+                LOG.error(_("Property set failed"))
                 result += 1
 
         if parsed_args.state:
@@ -145,7 +145,7 @@ remaining arguments are set using the ``update()`` method.
                     parsed_args.state,
                 )
             except SomeException:      # Need to define the exceptions to catch here
-                self.app.log.error("State set failed")
+                LOG.error(_("State set failed"))
                 result += 1
 
         try:
@@ -154,7 +154,7 @@ remaining arguments are set using the ``update()`` method.
                 **kwargs
             )
         except SomeException:      # Need to define the exceptions to catch here
-            self.app.log.error("Update failed")
+            LOG.error(_("Update failed"))
             result += 1
 
         # NOTE(dtroyer): We need to signal the error, and a non-zero return code,
@@ -166,8 +166,8 @@ Example 2
 ~~~~~~~~~
 
 This example is taken from the ``network delete`` command which takes multiple
-networks to delete. All networks will be delete in a loop, which makes multiple
-``delete_network()`` calls.
+networks to delete. All networks will be deleted in a loop, which makes
+multiple ``delete_network()`` calls.
 
 .. code-block:: python
 
@@ -179,7 +179,7 @@ networks to delete. All networks will be delete in a loop, which makes multiple
                 'network',
                 metavar="<network>",
                 nargs="+",
-                help=("Network(s) to delete (name or ID)")
+                help=_("Network(s) to delete (name or ID)")
             )
             return parser
 
@@ -191,11 +191,15 @@ networks to delete. All networks will be delete in a loop, which makes multiple
                     obj = client.find_network(network, ignore_missing=False)
                     client.delete_network(obj)
                 except Exception:
-                    self.app.log.error("Failed to delete network with name "
-                                       "or ID %s." % network)
+                    LOG.error(_("Failed to delete network with name "
+                                "or ID %s."), network)
                     ret += 1
 
             if ret > 0:
                 total = len(parsed_args.network)
-                msg = "Failed to delete %s of %s networks." % (ret, total)
+                msg = _("Failed to delete %(ret)s of %(total)s networks.") %
+                    {
+                        "ret": ret,
+                        "total": total,
+                    }
                 raise exceptions.CommandError(msg)