tox: Update to pylint 1.5.1.

* Don't emit unsubscriptable-object if the node is found
  inside an abstract class.

* Add wrong-import-position to check_messages's decorator arguments
  for ImportChecker.leave_module

  This fixes an esoteric bug which occurs when ungrouped-imports and
  wrong-import-order are disabled and pylint is executed on multiple files.
  What happens is that without wrong-import-position in check_messages,
  leave_module will never be called, which means that the first non-import node
  from other files might leak into the current file,
  leading to wrong-import-position being emitted by pylint.

* Fix a crash which occurred when old visit methods are encountered
  in plugin modules.

* Don't emit import-self and cyclic-import for relative imports
  of modules with the same name as the package itself.

tox.ini

@@ -106,7 +106,7 @@ deps =
     {[testenv]deps}
     {[testenv:misc]deps}
     astroid==1.4.1
-    pylint==1.5.0
+    pylint==1.5.1
     requests==2.8.1
 commands =
     {envpython} scripts/link_pyqt.py --tox {envdir}