Exclude UserDict when deep reloading NumPy.

This prevents another test failure in IPython.lib.tests.test_irunner_pylab_magic::

    Traceback (most recent call last):
    ...
      File "/usr/lib/python2.7/weakref.py", line 53, in __init__
        UserDict.UserDict.__init__(self, *args, **kw)
    TypeError: unbound method __init__() must be called with UserDict instance as first argument (got WeakValueDictionary instance instead)

Closes  #1636.

IPython/lib/tests/test_deepreload.py

@@ -1,53 +1,53 b''
 # -*- coding: utf-8 -*-
 """Test suite for the deepreload module."""
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import os
 import sys
 
 import nose.tools as nt
 
 from IPython.testing import decorators as dec
 from IPython.utils.syspathcontext import prepended_to_syspath
 from IPython.utils.tempdir import TemporaryDirectory
 from IPython.lib.deepreload import reload as dreload
 
 #-----------------------------------------------------------------------------
 # Test functions begin
 #-----------------------------------------------------------------------------
 
 @dec.skipif_not_numpy
 def test_deepreload_numpy():
     "Test that NumPy can be deep reloaded."
     import numpy
     exclude = [
         # Standard exclusions:
         'sys', 'os.path', '__builtin__', '__main__',
         # Test-related exclusions:
-        'unittest',
+        'unittest', 'UserDict',
         ]
     dreload(numpy, exclude=exclude)
 
 def test_deepreload():
     "Test that dreload does deep reloads and skips excluded modules."
     with TemporaryDirectory() as tmpdir:
         with prepended_to_syspath(tmpdir):
             with open(os.path.join(tmpdir, 'A.py'), 'w') as f:
                 f.write("class Object(object):\n    pass\n")
             with open(os.path.join(tmpdir, 'B.py'), 'w') as f:
                 f.write("import A\n")
             import A
             import B
 
             # Test that A is not reloaded.
             obj = A.Object()
             dreload(B, exclude=['A'])
             nt.assert_true(isinstance(obj, A.Object))
 
             # Test that A is reloaded.
             obj = A.Object()
             dreload(B)
             nt.assert_false(isinstance(obj, A.Object))