Clarify batch file ERROR: message
diff --git a/youtube_dl/__init__.py b/youtube_dl/__init__.py
index 165c975dd75..9a659fc654d 100644
--- a/youtube_dl/__init__.py
+++ b/youtube_dl/__init__.py
@@ -94,7 +94,7 @@ def _real_main(argv=None):
             if opts.verbose:
                 write_string('[debug] Batch file urls: ' + repr(batch_urls) + '\n')
         except IOError:
-            sys.exit('ERROR: batch file could not be read')
+            sys.exit('ERROR: batch file %s could not be read' % opts.batchfile)
     all_urls = batch_urls + [url.strip() for url in args]  # batch_urls are already striped in read_batch_urls
     _enc = preferredencoding()
     all_urls = [url.decode(_enc, 'ignore') if isinstance(url, bytes) else url for url in all_urls]

Adding the name of the file which couldn't be read & a brief description of the option.

Just "ERROR: batch file could not be read" can be confusing for users who are inexperienced (and likely using Windows).

eg. https://www.reddit.com/r/Piracy/comments/cfl0ap/youtubedl_error_batch_file_could_not_be_read_how/
(The user specified option -audio-file, instead of --audio-file)

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