download: use requests session to enable connection pooling

setup.py

@@ -89,6 +89,7 @@ setup(
     namespace_packages = ['zc'],
     install_requires = [
         'setuptools>=8.0',
+        'requests',
     ],
     include_package_data = True,
     entry_points = entry_points,

src/zc/buildout/download.py

@@ -31,28 +31,15 @@ try:
 
 except ImportError:
     # Python 2
-    import base64
     from urlparse import urlparse
-    from urlparse import urlunparse
-    import urllib2
-
+    # use requests for connection pooling
+    import requests
+    session = requests.Session()
     def urlretrieve(url, tmp_path):
-        """Work around Python issue 24599 includig basic auth support
-        """
-        scheme, netloc, path, params, query, frag = urlparse(url)
-        auth, host = urllib2.splituser(netloc)
-        if auth:
-            url = urlunparse((scheme, host, path, params, query, frag))
-            req = urllib2.Request(url)
-            base64string = base64.encodestring(auth)[:-1]
-            basic = "Basic " + base64string
-            req.add_header("Authorization", basic)
-        else:
-            req = urllib2.Request(url)
-        url_obj = urllib2.urlopen(req)
-        with open(tmp_path, 'wb') as fp:
-            fp.write(url_obj.read())
-        return tmp_path, url_obj.info()
+       r = session.get(url)
+       with open(tmp_path, 'wb') as fp:
+         fp.write(r.content)
+       return tmp_path, r
 
 
 from zc.buildout.easy_install import realpath