[compat] Replace deficient ChainMap class in Py3.3 and earlier

* fix version check

Author: dirkf

youtube_dl/compat.py

@@ -3005,7 +3005,7 @@ def unpack(self, string):
 try:
     from collections import ChainMap as compat_collections_chain_map
     # Py3.3's ChainMap is deficient
-    if sys.version_info <= (3, 3):
+    if sys.version_info < (3, 4):
         raise ImportError
 except ImportError:
     # Py <= 3.3