Upgrade pip aggressively

fcollonval · fcollonval · commit 97471cc262be · 2021-07-20T15:00:01.000+02:00
diff --git a/postBuild b/postBuild
@@ -1,3 +1,4 @@
 jlpm
+python -m pip install -U pip
 jlpm run install-py
 jupyter serverextension enable jlab_ext_example
