support empty password for http_proxy config

scrapy/downloadermiddlewares/httpproxy.py

@@ -25,7 +25,7 @@ class HttpProxyMiddleware(object):
         proxy_type, user, password, hostport = _parse_proxy(url)
         proxy_url = urlunparse((proxy_type or orig_type, hostport, '', '', '', ''))
 
-        if user and password:
+        if user:
             user_pass = '%s:%s' % (unquote(user), unquote(password))
             creds = base64.b64encode(user_pass).strip()
         else:

tests/test_downloadermiddleware_httpproxy.py

@@ -54,6 +54,14 @@ class TestDefaultHeadersMiddleware(TestCase):
         self.assertEquals(req.meta, {'proxy': 'https://proxy:3128'})
         self.assertEquals(req.headers.get('Proxy-Authorization'), 'Basic dXNlcjpwYXNz')
 
+    def test_proxy_auth_empty_passwd(self):
+        os.environ['http_proxy'] = 'https://user:@proxy:3128'
+        mw = HttpProxyMiddleware()
+        req = Request('http://scrapytest.org')
+        assert mw.process_request(req, spider) is None
+        self.assertEquals(req.meta, {'proxy': 'https://proxy:3128'})
+        self.assertEquals(req.headers.get('Proxy-Authorization'), 'Basic dXNlcjo=')
+
     def test_proxy_already_seted(self):
         os.environ['http_proxy'] = http_proxy = 'https://proxy.for.http:3128'
         mw = HttpProxyMiddleware()