made output_filenames attribute in Reduce read-only as this is how it…

… behaves when used in the code.

recipe_system/reduction/coreReduce.py

@@ -114,14 +114,14 @@ def __init__(self, sys_args=None):
             import_module(args.adpkg)
 
         self.adinputs = None
-        self.output_filenames = None
         self.mode = args.mode
         self.drpkg = args.drpkg
         self.files = args.files
         self.suffix = args.suffix
         self.ucals = normalize_ucals(args.files, args.user_cal)
         self.uparms = set_btypes(args.userparam)
         self._upload = args.upload
+        self._output_filenames = None
         self.recipename = args.recipename if args.recipename else 'default'
 
     @property
@@ -138,6 +138,11 @@ def upload(self, upl):
             self._upload = upl
         return
 
+    @property
+    def output_filenames(self):
+        return self._output_filenames
+
+
     def runr(self):
         """
         Map and run the requested or defaulted recipe.
@@ -233,7 +238,7 @@ def runr(self):
                 xstat = signal.SIGABRT
 
         self._write_final(p.streams['main'])
-        self.output_filenames = [ad.filename for ad in p.streams['main']]
+        self._output_filenames = [ad.filename for ad in p.streams['main']]
 
         if xstat != 0:
             msg = "reduce instance aborted."