Fix test case and correct for the new results.

DoCommand.py

 import re
 
-import Command
+from Command import *
 from PrettyPrinter import *
 from Recurrence import advance_recurring_todo
 from TodoList import InvalidTodoException
 from Utils import convert_todo_number, InvalidTodoNumberException
 
-class DoCommand(Command.Command):
+class DoCommand(Command):
     def __init__(self, p_args, p_todolist,
                  p_out=lambda a: None,
                  p_err=lambda a: None,
@@ -18,7 +18,7 @@ class DoCommand(Command.Command):
         try:
             self.number = convert_todo_number(self.argument(0))
             self.todo = self.todolist.todo(self.number)
-        except (InvalidTodoNumberException, InvalidTodoException):
+        except (InvalidCommandArgument, InvalidTodoNumberException, InvalidTodoException):
             self.todo = None
 
     def _complete_children(self):

test/DoCommandTest.py

@@ -102,7 +102,7 @@ class DoCommandTest(CommandTest.CommandTest):
         self.assertEquals(self.errors, "Todo has already been completed.\n")
 
     def test_empty(self):
-        command = DoCommand.DoCommand([""], self.todolist, self.out, self.error)
+        command = DoCommand.DoCommand([], self.todolist, self.out, self.error)
         command.execute()
 
         self.assertFalse(self.todolist.is_dirty())