Remove imports of 'warnings' that are no longer needed in dummy_thread,
filecmp, and shelve.
diff --git a/Lib/dummy_thread.py b/Lib/dummy_thread.py
index 16dcf7e..198dc49 100644
--- a/Lib/dummy_thread.py
+++ b/Lib/dummy_thread.py
@@ -17,7 +17,6 @@
            'interrupt_main', 'LockType']
 
 import traceback as _traceback
-import warnings
 
 class error(Exception):
     """Dummy implementation of thread.error."""
diff --git a/Lib/filecmp.py b/Lib/filecmp.py
index 9885765..0b7ce16 100644
--- a/Lib/filecmp.py
+++ b/Lib/filecmp.py
@@ -11,7 +11,6 @@
 
 import os
 import stat
-import warnings
 from itertools import ifilter, ifilterfalse, imap, izip
 
 __all__ = ["cmp","dircmp","cmpfiles"]
diff --git a/Lib/shelve.py b/Lib/shelve.py
index 1f78fc1..fb41c84 100644
--- a/Lib/shelve.py
+++ b/Lib/shelve.py
@@ -69,7 +69,6 @@
     from StringIO import StringIO
 
 import UserDict
-import warnings
 
 __all__ = ["Shelf","BsdDbShelf","DbfilenameShelf","open"]
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 4a92186..99414d1 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -48,6 +48,8 @@
 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#'.