Don't check for wx in the test suite.

An interaction between wx and threads was blocking certain Unix signals,
causing an unrelated test to fail for me.

We were only checking for wx to exclude the inputhookwx module from the
test run. It contains no tests anyway, so we may as well just exclude it
in all cases.

IPython/testing/iptest.py

@@ -146,8 +146,6 b" have['cython'] = test_for('Cython')"
 have['oct2py'] = test_for('oct2py')
 have['tornado'] = test_for('tornado.version_info', (3,1,0), callback=None)
 have['jinja2'] = test_for('jinja2')
-have['wx'] = test_for('wx')
-have['wx.aui'] = test_for('wx.aui')
 have['azure'] = test_for('azure')
 have['requests'] = test_for('requests')
 have['sphinx'] = test_for('sphinx')
@@ -203,8 +201,6 b" if not have['matplotlib']:"
 
 # lib:
 sec = test_sections['lib']
-if not have['wx']:
-    sec.exclude('inputhookwx')
 if not have['pexpect']:
     sec.exclude('irunner')
     sec.exclude('tests.test_irunner')
@@ -213,6 +209,9 b" if not have['zmq']:"
 # We do this unconditionally, so that the test suite doesn't import
 # gtk, changing the default encoding and masking some unicode bugs.
 sec.exclude('inputhookgtk')
+# We also do this unconditionally, because wx can interfere with Unix signals.
+# There are currently no tests for it anyway.
+sec.exclude('inputhookwx')
 # Testing inputhook will need a lot of thought, to figure out
 # how to have tests that don't lock up with the gui event
 # loops in the picture