Fix autocompletion in prompt mode.

The completer would be instantiated before the todo list was loaded from
the file. Now, the completer is instantiated every time the todo list is
loaded.

topydo/cli/Prompt.py

@@ -56,6 +56,7 @@ class PromptApplication(CLIApplicationBase):
 
         self._process_flags()
         self.mtime = None
+        self.completer = None
 
     def _load_file(self):
         """
@@ -73,11 +74,12 @@ class PromptApplication(CLIApplicationBase):
             self.todolist = TodoList.TodoList(self.todofile.read())
             self.mtime = current_mtime
 
-    def run(self):
-        """ Main entry function. """
             # suppress upstream issue with Python 2.7
             # pylint: disable=no-value-for-parameter
-        completer = TopydoCompleter(self.todolist)
+            self.completer = TopydoCompleter(self.todolist)
+
+    def run(self):
+        """ Main entry function. """
         history = History()
 
         while True:
@@ -86,7 +88,7 @@ class PromptApplication(CLIApplicationBase):
 
             try:
                 user_input = get_input(u'topydo> ', history=history,
-                                       completer=completer).split()
+                                       completer=self.completer).split()
             except (EOFError, KeyboardInterrupt):
                 sys.exit(0)