Fix CI (#563)

PsiACE · web-flow · commit ab00a11b4735 · 2020-02-05T13:04:39.000+08:00
* Update tox.ini

`python -m pip install --upgrade pip`, to avoid permissions issues on windows CI.
diff --git a/tox.ini b/tox.ini
@@ -22,5 +22,5 @@ setenv =
 deps =
     -r{toxinidir}/requirements_dev.txt
 commands =
-    pip install -U pip
+    python -m pip install --upgrade pip
     pytest
