Run pylint on tests

Drop support for pylint < 1.0

Enable ignoring unknown attributes on modules (both nose and pytest
use advanced techniques, support for which only made it to pylint
recently)

Fix some bugs revealed by pylint

Do minor refactoring or add pylint:disable directives where the
linter complains.

Reviewed-By: Tomas Babej <tbabej@redhat.com>

ipatests/test_ipalib/test_plugable.py

@@ -21,6 +21,9 @@
 Test the `ipalib.plugable` module.
 """
 
+# FIXME: Pylint errors
+# pylint: disable=no-member
+
 import inspect
 from ipatests.util import raises, no_set, no_del, read_only
 from ipatests.util import getitem, setitem, delitem
@@ -343,7 +346,7 @@ def test_Registrar():
     orig1 = plugin1
     class base1_extended(Base1):
         pass
-    class plugin1(base1_extended):
+    class plugin1(base1_extended):  # pylint: disable=function-redefined
         pass
     e = raises(errors.PluginOverrideError, r, plugin1)
     assert e.base == 'Base1'