allow appveyor python3 builds to fail

.appveyor.yml

@@ -23,6 +23,16 @@ environment:
     - PYTHON: "C:\\Python35-x64"
       DISTUTILS_USE_SDK: "1"
 
+matrix:
+  allow_failures:
+      # we allow all python3 versions to fail without as they do not currently work
+    - PYTHON: "C:\\Python33"
+    - PYTHON: "C:\\Python33-x64"
+    - PYTHON: "C:\\Python34"
+    - PYTHON: "C:\\Python34-x64"
+    - PYTHON: "C:\\Python35"
+    - PYTHON: "C:\\Python35-x64"
+
 # tox-2.3.1 has a windows bug (#314), fixed in hg but not yet released. When
 # the next release comes out, replace this with just:
 #   %PYTHON%\python.exe -m pip install wheel tox