tox: Update pytest-mock to 0.11.0.

- PropertyMock is now accessible from mocker.
- Fix regression using one of the assert_* methods in patched functions which
  receive a parameter named method.

tox.ini

@@ -32,7 +32,7 @@ deps =
     pytest-cov==2.2.1
     pytest-faulthandler==1.3.0
     pytest-html==1.8.0
-    pytest-mock==0.10.1
+    pytest-mock==0.11.0
     pytest-qt==1.11.0
     pytest-instafail==0.3.0
     pytest-travis-fold==1.2.0