From a4b8b36b896c1ae5f8dbd04e75cb6a8d9d7f358b 2013-12-16 01:07:46
From: Thomas Kluyver <takowl@gmail.com>
Date: 2013-12-16 01:07:46
Subject: [PATCH] Also check that existing symlink has desired target before allowing it.

---

diff --git a/setupbase.py b/setupbase.py
index 219b1cb..6426d7b 100644
--- a/setupbase.py
+++ b/setupbase.py
@@ -381,7 +381,8 @@ class install_lib_symlink(Command):
         try:
             os.symlink(pkg, dest)
         except OSError as e:
-            if e.errno == errno.EEXIST and os.path.islink(dest):
+            if e.errno == errno.EEXIST and os.path.islink(dest) \
+                    and os.path.realpath(dest) == pkg:
                 print('Symlink already exists')
             else:
                 raise