Different behaviour between double quoted and single quoted string when using urllib in python

I am new to python and I learned there are no different between single and double quoted string. But I have found some different behavior.

from bs4 import BeautifulSoup
import urllib.request

url1 = "http://www.backpackers.com.tw/forum/forumdisplay.php?f=310"
url2 = 'http://www.backpackers.com.tw/forum/forumdisplay.php?f=310'

If I run:

response = urllib.request.urlopen(url1)

Result: Script finished without error

And If I run:

response = urllib.request.urlopen(url2)

Result: error

C:Usersuser1Desktopscrape>python backpacker_tw.py
Traceback (most recent call last):
  File "C:Python34liburllibrequest.py", line 1189, in do_open
    h.request(req.get_method(), req.selector, req.data, headers)
  File "C:Python34libhttpclient.py", line 1090, in request
    self._send_request(method, url, body, headers)
  File "C:Python34libhttpclient.py", line 1128, in _send_request
    self.endheaders(body)
  File "C:Python34libhttpclient.py", line 1086, in endheaders
    self._send_output(message_body)
  File "C:Python34libhttpclient.py", line 924, in _send_output
    self.send(msg)
  File "C:Python34libhttpclient.py", line 859, in send
    self.connect()
  File "C:Python34libhttpclient.py", line 836, in connect
    self.timeout, self.source_address)
  File "C:Python34libsocket.py", line 509, in create_connection
    raise err
  File "C:Python34libsocket.py", line 500, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [WinError 10061] No connection could be made because the
 target machine actively refused it

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "backpacker_tw.py", line 7, in <module>
    response = urllib.request.urlopen(url2)
  File "C:Python34liburllibrequest.py", line 153, in urlopen
    return opener.open(url, data, timeout)
  File "C:Python34liburllibrequest.py", line 455, in open
    response = self._open(req, data)
  File "C:Python34liburllibrequest.py", line 473, in _open
    '_open', req)
  File "C:Python34liburllibrequest.py", line 433, in _call_chain
    result = func(*args)
  File "C:Python34liburllibrequest.py", line 1215, in http_open
    return self.do_open(http.client.HTTPConnection, req)
  File "C:Python34liburllibrequest.py", line 1192, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error [WinError 10061] No connection could be ma
de because the target machine actively refused it>

Is it a bug or anything i missed?

C:Usersuser1Desktopscrape>python -V
Python 3.4.1