--- src/sage/misc/package.py.orig	2014-11-23 15:58:13.000000000 +0100
+++ src/sage/misc/package.py	2015-01-22 20:32:25.651383902 +0100
@@ -343,7 +343,7 @@
         sage: for pkg in list_packages('pip', local=True):
         ....:     assert not is_package_installed(pkg)
     """
-    return any(p.split('-')[0] == package for p in installed_packages(exclude_pip))
+    return True
 
 def package_versions(package_type, local=False):
     r"""
--- src/sage_setup/optional_extension.py.orig  2016-10-19 18:35:10.092577510 +0000
+++ src/sage_setup/optional_extension.py       2016-10-19 18:38:13.514765366 +0000
@@ -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):
     """
@@ -76,14 +74,7 @@
         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)
     else: