--- sage/src/sage_setup/optional_extension.py.orig	2016-09-02 21:28:28.584354231 +0200
+++ sage/src/sage_setup/optional_extension.py	2016-09-02 21:43:08.256305231 +0200
@@ -21,8 +21,6 @@
 from distutils.extension import Extension
 from sage.misc.package import is_package_installed, list_packages
 
-all_packages = list_packages(local=True)
-
 
 class CythonizeExtension(Extension):
     """
@@ -75,14 +73,7 @@
     try:
         condition = kwds.pop("condition")
     except KeyError:
-        pkg = kwds.pop("package")
-        try:
-            pkginfo = all_packages[pkg]
-        except KeyError:
-            # Might be an installed old-style package
-            condition = is_package_installed(pkg)
-        else:
-            condition = (pkginfo["installed_version"] == pkginfo["remote_version"])
+        condition = True
 
     if condition:
         return Extension(*args, **kwds)