[unpackfs] Log messages in English, too

- For debugging purposes, need to log the message in English before
   returning the (user-visible) error description.

src/modules/unpackfs/main.py

@@ -293,11 +293,13 @@ def run():
     root_mount_point = globalstorage.value("rootMountPoint")
 
     if not root_mount_point:
+        utils.warning("No mount point for root partition")
         return (_("No mount point for root partition"),
                 _("globalstorage does not contain a \"rootMountPoint\" key, "
                 "doing nothing"))
 
     if not os.path.exists(root_mount_point):
+        utils.warning("Bad root mount point \"{}\"".format(root_mount_point))
         return (_("Bad mount point for root partition"),
                 _("rootMountPoint is \"{}\", which does not "
                 "exist, doing nothing").format(root_mount_point))
@@ -311,16 +313,19 @@ def run():
         sourcefs = entry["sourcefs"]
 
         if sourcefs not in supported_filesystems:
+            utils.warning("The filesystem for \"{}\" ({}) is not supported".format(source, sourcefs))
             return (_("Bad unsquash configuration"),
                     _("The filesystem for \"{}\" ({}) is not supported").format(source, sourcefs))
 
         destination = os.path.abspath(root_mount_point + entry["destination"])
 
         if not os.path.exists(source):
+            utils.warning("The source filesystem \"{}\" does not exist".format(source))
             return (_("Bad unsquash configuration"),
                     _("The source filesystem \"{}\" does not exist").format(source))
 
         if not os.path.isdir(destination):
+            utils.warning(("The destination \"{}\" in the target system is not a directory").format(destination))
             return (_("Bad unsquash configuration"),
                     _("The destination \"{}\" in the target system is not a directory").format(destination))