bpo-29972: Skip tests known to fail on AIX (#979)

* bpo-29972: Fix test_eintr on AIX

On AIX, sigtimedwait(0.2) sleeps 199.8 ms, whereas the test expects
200 ms or longer.

* bpo-29972: Skip some inet_pton() tests on AIX

Skip some inet_pton() tests of test_socket on AIX.

inet_pton() on AIX is less strict than on Linux and doesn't reject
some invalid IP addresses. The unit tests test more the libc than
Python itself.

* bpo-29972: Skip tests known to fail on AIX

* test_locale.test_strcoll_with_diacritic()
* test_locale.test_strxfrm_with_diacritic()
* test_strptime.test_week_of_year_and_day_of_week_calculation()
* test_tools.test_POT_Creation_Date()

Lib/test/test_tools/test_i18n.py

@@ -1,6 +1,7 @@
 """Tests to cover the Tools/i18n package"""
 
 import os
+import sys
 import unittest
 
 from test.support.script_helper import assert_python_ok
@@ -53,7 +54,8 @@ class Test_pygettext(unittest.TestCase):
 
             #"Plural-Forms" is optional
 
-
+    @unittest.skipIf(sys.platform.startswith('aix'),
+                     'bpo-29972: broken test on AIX')
     def test_POT_Creation_Date(self):
         """ Match the date format from xgettext for POT-Creation-Date """
         from datetime import datetime