title: deferred.defer shows PermanentTaskFailure: maximum recursion depth exceeded
body: <p>I'm trying to import all the data from a csv file and stored it to the datastore as csv file..</p>
  
  <p><code>__init__.py</code> file where <code>app</code> is defined.</p>
  
  <pre><code>@app.route("/import/&lt;model&gt;", methods=['POST'])
  def import_csv(model):
      reader = UsersImporter(fil, user)
      reader.read()
  </code></pre>
  
  <p><code>importers.py</code></p>
  
  <pre><code>class UsersImporter(BaseImporter):
      def read(self):
          line = self.file.readline()
          self.checking_delimiter_on_first_line(line)
          self.file.seek(0)
          reader = csv.DictReader(self.file, delimiter=self.delimiter)
          try:
              for row in reader:
                  deferred.defer(self.parse_line, row)
          except:
              print traceback.format_exc()
          self.insert_entities()
  </code></pre>
  
  <p>Above code produces the below traceback.</p>
  
  <pre><code>INFO     2016-12-26 08:00:09,745 deferred.py:303] X-Appengine-Current-Namespace:, X-Appengine-Taskexecutioncount:0, X-Appengine-Country:ZZ, X-Appengine-Taskname:task8, X-Appengine-Taskretrycount:0, X-Appengine-Queuename:default, X-Appengine-Tasketa:1482739209.69
  ERROR    2016-12-26 08:00:09,749 deferred.py:319] Permanent failure attempting to execute task
  Traceback (most recent call last):
    File "/home/gemini/softwares/google_appengine/google/appengine/ext/deferred/deferred.py", line 310, in post
      self.run_from_request()
    File "/home/gemini/softwares/google_appengine/google/appengine/ext/deferred/deferred.py", line 305, in run_from_request
      run(self.request.body)
    File "/home/gemini/softwares/google_appengine/google/appengine/ext/deferred/deferred.py", line 145, in run
      raise PermanentTaskFailure(e)
  PermanentTaskFailure: maximum recursion depth exceeded
  </code></pre>
  
  <p>You see, <code>row</code> is not an instance of <code>requestHandler</code> class. And also <code>self.parse_line</code> is a method defined in the <code>BaseImporter</code>.</p>