Fixed #6547: Added the ignore_dangling_symlinks option to shutil.copytree
diff --git a/Lib/test/test_shutil.py b/Lib/test/test_shutil.py
index dfa6f9f..f6b047e 100644
--- a/Lib/test/test_shutil.py
+++ b/Lib/test/test_shutil.py
@@ -13,7 +13,7 @@
 from distutils.spawn import find_executable, spawn
 from shutil import (_make_tarball, _make_zipfile, make_archive,
                     register_archive_format, unregister_archive_format,
-                    get_archive_formats)
+                    get_archive_formats, Error)
 import tarfile
 import warnings
 
@@ -351,6 +351,26 @@
         shutil.copytree(src_dir, dst_dir, copy_function=_copy)
         self.assertEquals(len(copied), 2)
 
+    def test_copytree_dangling_symlinks(self):
+
+        # a dangling symlink raises an error at the end
+        src_dir = self.mkdtemp()
+        dst_dir = os.path.join(self.mkdtemp(), 'destination')
+        os.symlink('IDONTEXIST', os.path.join(src_dir, 'test.txt'))
+        os.mkdir(os.path.join(src_dir, 'test_dir'))
+        self._write_data(os.path.join(src_dir, 'test_dir', 'test.txt'), '456')
+        self.assertRaises(Error, shutil.copytree, src_dir, dst_dir)
+
+        # a dangling symlink is ignored with the proper flag
+        dst_dir = os.path.join(self.mkdtemp(), 'destination2')
+        shutil.copytree(src_dir, dst_dir, ignore_dangling_symlinks=True)
+        self.assertNotIn('test.txt', os.listdir(dst_dir))
+
+        # a dangling symlink is copied if symlinks=True
+        dst_dir = os.path.join(self.mkdtemp(), 'destination3')
+        shutil.copytree(src_dir, dst_dir, symlinks=True)
+        self.assertIn('test.txt', os.listdir(dst_dir))
+
     @unittest.skipUnless(zlib, "requires zlib")
     def test_make_tarball(self):
         # creating something to tar