[gen:wiki] raise explicit error message if botpassword is not defined

lib/refrepo/gen/wiki/wiki_generator.rb

@@ -16,8 +16,11 @@ class WikiGenerator
     tries = 3
     begin
       conf = RefRepo::Utils.get_api_config
-      @mw_client.log_in(conf['username'], conf['botpassword'])
+      @mw_client.log_in(conf[:username], conf[:botpassword])
     rescue
+      if !conf.has_key?(:botpassword)
+        raise "botpassword is not defined, see https://www.grid5000.fr/w/TechTeam:Reference_Repository#Credentials"
+      end
       tries -= 1
       if tries > 0
         puts "Login failed. retrying..."