Issue #4489: Rename the feature marker for the symlink resistant rmtree and store it as a function attribute
diff --git a/Lib/shutil.py b/Lib/shutil.py
index f743d05..2c00f4a 100644
--- a/Lib/shutil.py
+++ b/Lib/shutil.py
@@ -405,8 +405,9 @@
     except os.error:
         onerror(os.rmdir, path, sys.exc_info())
 
-rmtree_is_safe = _use_fd_functions = (os.unlink in os.supports_dir_fd and
-                                      os.open in os.supports_dir_fd)
+_use_fd_functions = (os.unlink in os.supports_dir_fd and
+                     os.open in os.supports_dir_fd)
+
 def rmtree(path, ignore_errors=False, onerror=None):
     """Recursively delete a directory tree.
 
@@ -449,6 +450,9 @@
     else:
         return _rmtree_unsafe(path, onerror)
 
+# Allow introspection of whether or not the hardening against symlink
+# attacks is supported on the current platform
+rmtree.avoids_symlink_attacks = _use_fd_functions
 
 def _basename(path):
     # A basename() variant which first strips the trailing slash, if present.