CI(appveyor.yml): Upgrade `pip` using `python -m pip`

Avoid `WindowsError: [Error 5] Access is denied`.

diff --git a/appveyor.yml b/appveyor.yml
index 9d556da2c9ee45217837ebdc061e3cf1b4b50ae2..1a2ca615581677cc2df4f28483df4255733857cf 100644 (file)
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -65,8 +65,9 @@ install:
   - "SET TOXPYTHON=%PYTHON_HOME%\\python.exe"
   - "python --version"
   - "python -c \"import struct; print(struct.calcsize('P') * 8)\""
+  - "python -m pip install --upgrade pip setuptools"
+  - "pip install --upgrade tox ppu"
   - "pip --version"
-  - "pip install --upgrade pip setuptools tox ppu"
 
 # No build step - we don't have C extensions
 build: false