Without this patch `virtualenv --python=python2.7 .` fails with an error because it notices that the python readline.so is not in the same path as python2.7. I assume this is to avoid copying the wrong file on systems where it is possible to find incompatible libraries by accident. Adding "/nix/store" to the prefix fixes this problem. Unfortunately readline is still not available if you just run `virtualenv .`.


--- virtualenv-1.6.4/virtualenv.py	2012-05-20 00:40:38.070649647 +0200
+++ virtualenv-1.6.4/virtualenv.py	2012-05-20 00:45:10.596242604 +0200
@@ -951,13 +951,7 @@
 
 
 def change_prefix(filename, dst_prefix):
-    prefixes = [sys.prefix]
-
-    if sys.platform == "darwin":
-        prefixes.extend((
-            os.path.join("/Library/Python", sys.version[:3], "site-packages"),
-            os.path.join(sys.prefix, "Extras", "lib", "python"),
-            os.path.join("~", "Library", "Python", sys.version[:3], "site-packages")))
+    prefixes = ["/nix/store", sys.prefix]
 
     if hasattr(sys, 'real_prefix'):
         prefixes.append(sys.real_prefix)
@@ -968,6 +962,8 @@
             _, relpath = filename.split(src_prefix, 1)
             assert relpath[0] == os.sep
             relpath = relpath[1:]
+            if src_prefix == "/nix/store":
+                relpath = "/".join(relpath.split("/")[1:])
             return join(dst_prefix, relpath)
     assert False, "Filename %s does not start with any of these prefixes: %s" % \
         (filename, prefixes)