fixing deprecation warnings with argh

When I run watchmedo, it throws a whole load of deprecation warnings.

Just added the relevant decorator changes to make those go away.

src/watchdog/watchmedo.py

@@ -36,7 +36,7 @@
     except ImportError:
         from io import StringIO
 
-from argh import arg, alias, ArghParser
+from argh import arg, aliases, ArghParser, expects_obj
 from watchdog.version import VERSION_STRING
 from watchdog.utils import load_class
 from pathtools.path import absolute_path, parent_dir_path
@@ -152,7 +152,7 @@ def schedule_tricks(observer, tricks, pathname, recursive):
             observer.schedule(handler, trick_pathname, recursive)
 
 
-@alias('tricks')
+@aliases('tricks')
 @arg('files',
      nargs='*',
      help='perform tricks from given file')
@@ -167,6 +167,7 @@ def schedule_tricks(observer, tricks, pathname, recursive):
 @arg('--recursive',
      default=True,
      help='recursively monitor paths')
+@expects_obj
 def tricks_from(args):
     """
     Subcommand to execute tricks from a tricks configuration file.
@@ -211,7 +212,7 @@ def tricks_from(args):
         o.join()
 
 
-@alias('generate-tricks-yaml')
+@aliases('generate-tricks-yaml')
 @arg('trick_paths',
      nargs='*',
      help='Dotted paths for all the tricks you want to generate')
@@ -228,6 +229,7 @@ def tricks_from(args):
      default=False,
      help='if --append-to-file is not specified, produces output for \
 appending instead of a complete tricks yaml file.')
+@expects_obj
 def tricks_generate_yaml(args):
     """
     Subcommand to generate Yaml configuration for tricks named on the command
@@ -314,6 +316,7 @@ def tricks_generate_yaml(args):
 @arg('--debug-force-inotify',
      default=False,
      help='[debug] forces Linux inotify(7)')
+@expects_obj
 def log(args):
     """
     Subcommand to log file system events to the console.
@@ -418,6 +421,7 @@ def log(args):
      default=False,
      help="Ignore events that occur while command is still being executed " \
           "to avoid multiple simultaneous instances")
+@expects_obj
 def shell_command(args):
     """
     Subcommand to execute shell commands in response to file system events.
@@ -497,6 +501,7 @@ def shell_command(args):
      default=10.0,
      help='when stopping, kill the subprocess after the specified timeout '
           '(default 10)')
+@expects_obj
 def auto_restart(args):
     """
     Subcommand to start a long-running subprocess and restart it