Explicit definition needed despite being an empty value.

Tests do pass in https://nexedi.erp5.net/test_result_module/20170530-4EB92D8F/view

/reviewed-on !168

software/ipython_notebook/instance.cfg.in

@@ -109,6 +109,7 @@ filename = knowledge0.cfg
 [read-knowledge0]
 recipe = slapos.cookbook:zero-knowledge.read
 filename = knowledge0.cfg
+password =
 
 [monitor-instance-parameter]
 monitor-base-url = ${monitor-frontend-promise:url}

software/ipython_notebook/software.cfg

@@ -64,7 +64,7 @@ recipe = slapos.recipe.template:jinja2
 template = ${:_profile_base_location_}/instance.cfg.in
 rendered = ${buildout:directory}/template.cfg
 mode = 0644
-md5sum = b6555d25fd89bf92f47eda60a29c2b44
+md5sum = b564e553811db272be681c331b270bbe
 context =
   key bin_directory buildout:bin-directory
   key develop_eggs_directory buildout:develop-eggs-directory