Still no go with pip 10. Try to simplify and build psutil.

appveyor.yml

@@ -124,14 +124,8 @@ 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
-  # Note that psutil won't build under PyPy on Windows.
-  - "%CMD_IN_ENV% %PYEXE% -m pip install -U cython zope.interface zope.event"
-  - "%CMD_IN_ENV% %PYEXE% -m pip install -U setuptools wheel greenlet cffi dnspython idna requests"
+  - "%CMD_IN_ENV% %PYEXE% -m pip install -U -r ci-requirements.txt"
 
-  - ps:
-      if ("${env:PYTHON_ID}" -ne "pypy") {
-         pip install psutil | Out-Null;
-      }
   - ps: "if(Test-Path(\"${env:PYTHON}\\bin\")) {ls ${env:PYTHON}\\bin;}"
   - ps: "if(Test-Path(\"${env:PYTHON}\\Scripts\")) {ls ${env:PYTHON}\\Scripts;}"