Revert pypa#2636 - It caused issues when stdlib things were dependencies

CHANGES.txt

@@ -1,3 +1,9 @@
+**6.1.1 (2015-04-07)**
+
+* No longer ignore dependencies which have been added to the standard library,
+  instead continue to install them.
+
+
 **6.1.0 (2015-04-07)**
 
 * Fixes :issue:`2502`. Upgrades were failing when no potential links were found

pip/req/req_set.py

@@ -6,7 +6,6 @@
 import logging
 import os
 
-from pip.compat import stdlib_pkgs
 from pip._vendor import pkg_resources
 from pip._vendor import requests
 
@@ -134,17 +133,6 @@ def prep_for_dist(self):
         pass
 
 
-def _skip_req(req):
-    if req.name in stdlib_pkgs:
-        logger.warning(
-            "Skipping requirement: %s because %s is a stdlib package",
-            req,
-            req.name,
-        )
-        return True
-    return False
-
-
 class RequirementSet(object):
 
     def __init__(self, build_dir, src_dir, download_dir, upgrade=False,
@@ -220,9 +208,6 @@ def add_requirement(self, install_req, parent_req_name=None):
                          install_req.name, install_req.markers)
             return []
 
-        if _skip_req(install_req):
-            return []
-
         install_req.as_egg = self.as_egg
         install_req.use_user_site = self.use_user_site
         install_req.target_dir = self.target_dir
@@ -302,9 +287,6 @@ def _walk_req_to_install(self, handler):
             list(self.unnamed_requirements), list(self.requirements.values()),
             discovered_reqs)
         for req_to_install in reqs:
-            if _skip_req(req_to_install):
-                continue
-
             more_reqs = handler(req_to_install)
             if more_reqs:
                 discovered_reqs.extend(more_reqs)