Use HTTPS for PyPI index

We are preparing a new buildout version nexedi/slapos.buildout!12

but until that we can force the default index in profiles

/reviewed-on nexedi/slapos!248

stack/slapos.cfg

@@ -53,6 +53,9 @@ allow-hosts +=
   www.dabeaz.com
   www.owlfish.com
 
+# Use an https index
+index = https://pypi.python.org/simple/
+
 # XXX: Workaround of SlapOS limitation
 # Unzippig of eggs is required, as SlapOS do not yet provide nicely working
 # development / fast switching environment for whole software