[YoutubeDL] Include rtmpdump in exe versions -v output

youtube_dl/downloader/rtmp.py

@@ -12,9 +12,15 @@ from ..utils import (
     compat_str,
     encodeFilename,
     format_bytes,
+    get_exe_version,
 )
 
 
+def rtmpdump_version():
+    return get_exe_version(
+        'rtmpdump', ['--help'], r'(?i)RTMPDump\s*v?([0-9a-zA-Z._-]+)')
+
+
 class RtmpFD(FileDownloader):
     def real_download(self, filename, info_dict):
         def run_rtmpdump(args):