YoutubeDL: Make the decision about removing the original file after each postprocessor is run (fixes #2261)

If one of the processors said the file should be kept, it wouldn't pay
attention to the response from the following processors. This was wrong if the
'keep_video' option was False, if the first extractor modifies the original file
and then we extract its audio we don't want to keep the original video file.

youtube_dl/YoutubeDL.py

@@ -1235,14 +1235,15 @@ class YoutubeDL(object):
         """Run all the postprocessors on the given file."""
         info = dict(ie_info)
         info['filepath'] = filename
-        keep_video = None
         pps_chain = []
         if ie_info.get('__postprocessors') is not None:
             pps_chain.extend(ie_info['__postprocessors'])
         pps_chain.extend(self._pps)
         for pp in pps_chain:
+            keep_video = None
+            old_filename = info['filepath']
             try:
-                keep_video_wish, new_info = pp.run(info)
+                keep_video_wish, info = pp.run(info)
                 if keep_video_wish is not None:
                     if keep_video_wish:
                         keep_video = keep_video_wish
@@ -1251,12 +1252,12 @@ class YoutubeDL(object):
                         keep_video = keep_video_wish
             except PostProcessingError as e:
                 self.report_error(e.msg)
-        if keep_video is False and not self.params.get('keepvideo', False):
-            try:
-                self.to_screen('Deleting original file %s (pass -k to keep)' % filename)
-                os.remove(encodeFilename(filename))
-            except (IOError, OSError):
-                self.report_warning('Unable to remove downloaded video file')
+            if keep_video is False and not self.params.get('keepvideo', False):
+                try:
+                    self.to_screen('Deleting original file %s (pass -k to keep)' % old_filename)
+                    os.remove(encodeFilename(old_filename))
+                except (IOError, OSError):
+                    self.report_warning('Unable to remove downloaded video file')
 
     def _make_archive_id(self, info_dict):
         # Future-proof against any change in case