Index: make.py
==================================================================
--- make.py
+++ make.py
@@ -231,11 +231,11 @@
 
 
 def createFirefoxExtension (sLang, dVars):
     "create extension for Firefox"
     print("Building extension for Firefox")
-    eraseFolder("_build/xpi/"+sLang)
+    createCleanFolder("_build/xpi/"+sLang)
     dir_util.copy_tree("gc_lang/"+sLang+"/xpi/", "_build/xpi/"+sLang)
     dir_util.copy_tree("grammalecte-js", "_build/xpi/"+sLang+"/grammalecte")
     sHTML, dProperties = createOptionsForFirefox(dVars)
     dVars['optionsHTML'] = sHTML
     copyAndFileTemplate("_build/xpi/"+sLang+"/data/about_panel.html", "_build/xpi/"+sLang+"/data/about_panel.html", dVars)