Work around setuptools bug not catching some network timeouts

This fixes random failures when running in newest mode (which is the default
case), or when the requested version is available in the download-cache.

src/zc/buildout/easy_install.py

@@ -31,6 +31,7 @@ import setuptools.command.easy_install
 import setuptools.command.setopt
 import setuptools.package_index
 import shutil
+import socket
 import stat
 import subprocess
 import sys
@@ -151,6 +152,19 @@ class AllowHostsPackageIndex(setuptools.package_index.PackageIndex):
         self._current_requirement = str(requirement)
         return super(AllowHostsPackageIndex, self).find_packages(requirement)
 
+    def open_url(self, url, warning=None):
+        # setuptools (or urllib?) bug: There are already so many exceptions
+        # catched, like socket errors (e.g. failure in name resolution) or
+        # HTTP errors. Depending on when a timeout occurs, it is either catched
+        # (URLError during the SSL handshake) or not (socket.error while
+        # getting a HTTP response).
+        try:
+            return super(AllowHostsPackageIndex, self).open_url(url, warning)
+        except socket.error, e:
+            if not warning:
+                raise
+            self.warn(warning, e)
+
     def process_url(self, url, retrieve=False):
         """Evaluate a URL as a possible download, and maybe retrieve it"""
         if url in self.scanned_urls and not retrieve: