Remove imports of 'warnings' that are no longer needed in dummy_thread,

filecmp, and shelve.

Lib/dummy_thread.py

@@ -17,7 +17,6 @@ __all__ = ['error', 'start_new_thread', 'exit', 'get_ident', 'allocate_lock',
            'interrupt_main', 'LockType']
 
 import traceback as _traceback
-import warnings
 
 class error(Exception):
     """Dummy implementation of thread.error."""

Lib/filecmp.py

@@ -11,7 +11,6 @@ Functions:
 
 import os
 import stat
-import warnings
 from itertools import ifilter, ifilterfalse, imap, izip
 
 __all__ = ["cmp","dircmp","cmpfiles"]

Lib/shelve.py

@@ -69,7 +69,6 @@ except ImportError:
     from StringIO import StringIO
 
 import UserDict
-import warnings
 
 __all__ = ["Shelf","BsdDbShelf","DbfilenameShelf","open"]
 

Misc/NEWS

@@ -48,6 +48,8 @@ Core and Builtins
 Library
 -------
 
+- Remove unneeded imports of 'warnings' from shelve, filecmp, and dummy_thread.
+
 - Issue #3575: Incremental decoder's decode function now takes bytearray
   by using 's*' instead of 't#'.