s/dev\/null/os.devnull + add binary flag

For windows compatibility

weboob/applications/radioob/radioob.py

@@ -199,7 +199,7 @@ class Radioob(ReplApplication):
         audio.url = _obj.url
 
         def check_exec(executable):
-            with open('/dev/null', 'w') as devnull:
+            with open(os.devnull, 'w') as devnull:
                 process = subprocess.Popen(['which', executable], stdout=devnull)
                 if process.wait() != 0:
                     print('Please install "%s"' % executable, file=self.stderr)