Fix argument checking in gcl.py

Otherwise, commands like "gcl commit" would throw an exception instead of a comprehensible error message.

TBR=jam

Review URL: http://codereview.chromium.org/2366002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@48520 0039d316-1c4b-4281-b951-d872f2087c98

gcl.py

@@ -667,6 +667,8 @@ def need_change(function):
 def need_change_and_args(function):
   """Converts args -> change_info."""
   def hook(args):
+    if not args:
+      ErrorExit("You need to pass a change list name")
     change_info = ChangeInfo.Load(args.pop(0), GetRepositoryRoot(), True, True)
     return function(change_info, args)
   defer_attributes(function, hook)