Skip import irunner test on Windows.

Closes gh-3544

IPython/lib/tests/test_imports.py

@@ -1,4 +1,5 b''
 # encoding: utf-8
+from IPython.testing import decorators as dec
 
 def test_import_backgroundjobs():
     from IPython.lib import backgroundjobs
@@ -9,5 +10,6 b' def test_import_deepreload():'
 def test_import_demo():
     from IPython.lib import demo
 
[e-mail]_win32
 def test_import_irunner():
     from IPython.lib import irunner