UnicodeDecodeError when get help of temp option of compensationdelay filter.

[pengzhendong]

$ ffmpeg -h filter=compensationdelay

Filter compensationdelay
  Audio Compensation Delay Line.
    Inputs:
       #0: default (audio)
    Outputs:
       #0: default (audio)
compensationdelay AVOptions:
   mm                <int>        ..F.A....T. set mm distance (from 0 to 10) (default 0)
   cm                <int>        ..F.A....T. set cm distance (from 0 to 100) (default 0)
   m                 <int>        ..F.A....T. set meter distance (from 0 to 100) (default 0)
   dry               <double>     ..F.A....T. set dry amount (from 0 to 1) (default 0)
   wet               <double>     ..F.A....T. set wet amount (from 0 to 1) (default 1)
   temp              <int>        ..F.A....T. set temperature °C (from -50 to 50) (default 20)

File "av/option.pyx", line 73, in av.option.BaseOption.help.__get__
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2 in position 16: ordinal not in range(128)