Flask app get "IOError: [Errno 32] Broken pipe"

everyone,Now I use flask to develop web app.

But at first it works well,after operating web page for a while,the flask back-end shows error like these:

   File "/usr/lib64/python2.6/BaseHTTPServer.py", line 329, in handle
    self.handle_one_request()
  File "/usr/lib/python2.6/site-packages/werkzeug/serving.py", line 251, in handle_one_request
    return self.run_wsgi()
  File "/usr/lib/python2.6/site-packages/werkzeug/serving.py", line 193, in run_wsgi
    execute(self.server.app)
  File "/usr/lib/python2.6/site-packages/werkzeug/serving.py", line 184, in execute
    write(data)
  File "/usr/lib/python2.6/site-packages/werkzeug/serving.py", line 152, in write
    self.send_header(key, value)
  File "/usr/lib64/python2.6/BaseHTTPServer.py", line 390, in send_header
    self.wfile.write("%s: %s\r\n" % (keyword, value))
IOError: [Errno 32] Broken pipe

But I really don't know where is the wrong,I use session['eamil'] = request.form['eamil'] and in other file I use email = session.get('email').

Is this usage right?

or any other season cause this error ?

Please help me,thks.