Remove unneeded imports of 'warnings'.

Lib/test/test_exceptions.py

@@ -3,7 +3,6 @@
 import os
 import sys
 import unittest
-import warnings
 import pickle, cPickle
 
 from test.test_support import TESTFN, unlink, run_unittest

Lib/test/test_repr.py

@@ -136,7 +136,6 @@ class ReprTests(unittest.TestCase):
             '<built-in method split of str object at 0x'))
 
     def test_xrange(self):
-        import warnings
         eq = self.assertEquals
         eq(repr(xrange(1)), 'xrange(1)')
         eq(repr(xrange(1, 2)), 'xrange(1, 2)')