Disable psutil since it doesn't build.

appveyor.yml

@@ -119,7 +119,8 @@ install:
   # compiled extensions and are not provided as pre-built wheel packages,
   # pip will build them from source using the MSVC compiler matching the
   # target Python version and architecture
-  - "%CMD_IN_ENV% pip install -U wheel cython greenlet psutil cffi"
+  # Note that psutil won't build under PyPy on windows.
+  - "%CMD_IN_ENV% pip install -U wheel cython greenlet cffi"
 
   - ps: "if(Test-Path(\"${env:PYTHON}\\bin\")) {ls ${env:PYTHON}\\bin;}"
   - ps: "if(Test-Path(\"${env:PYTHON}\\Scripts\")) {ls ${env:PYTHON}\\Scripts;}"