title: How do I fix "AttributeError: 'NoneType' object has no attribute 'stdout'" when trying to write a CompositeVideoClip with moviepy?
body: <p>I am using the following:</p>
  
  <pre><code>from moviepy.editor import *
  
  ukulele = VideoFileClip("./clips/513732763.mp4")
  
  txt = TextClip("some text", color='white').set_duration(3)
  
  final = CompositeVideoClip([ukulele,txt])
  final.write_videofile("video.mp4",codec="libx264")
  </code></pre>
  
  <p>What I am trying to do is to add text over a video file clip. Writing normally with
  VideoFileClip is working, however, when using CompositeVideoClip it doesn't. 
  However, when running with Python 3.6.9 I get the following errors:</p>
  
  <pre><code>Moviepy - Building video video.mp4.
  MoviePy - Writing audio in videoTEMP_MPY_wvf_snd.mp3
  chunk:  12% 52/447 [00:00&lt;00:00, 518.22it/s, now=None]Traceback (most recent call last):
    File "main.py", line 8, in &lt;module&gt;
      final.write_videofile("video.mp4",codec="libx264")
    File "&lt;/usr/lib/python3.6/site-packages/decorator.py:decorator-gen-51&gt;", line 2, in write_videofile
    File "/usr/lib/python3.6/site-packages/moviepy/decorators.py", line 54, in requires_duration
      return f(clip, *a, **k)
    File "&lt;/usr/lib/python3.6/site-packages/decorator.py:decorator-gen-50&gt;", line 2, in write_videofile
    File "/usr/lib/python3.6/site-packages/moviepy/decorators.py", line 137, in use_clip_fps_by_default
      return f(clip, *new_a, **new_kw)
    File "&lt;/usr/lib/python3.6/site-packages/decorator.py:decorator-gen-49&gt;", line 2, in write_videofile
    File "/usr/lib/python3.6/site-packages/moviepy/decorators.py", line 22, in convert_masks_to_RGB
      return f(clip, *a, **k)
    File "/usr/lib/python3.6/site-packages/moviepy/video/VideoClip.py", line 317, in write_videofile
      logger=logger)
    File "&lt;/usr/lib/python3.6/site-packages/decorator.py:decorator-gen-73&gt;", line 2, in write_audiofile
    File "/usr/lib/python3.6/site-packages/moviepy/decorators.py", line 54, in requires_duration
      return f(clip, *a, **k)
    File "/usr/lib/python3.6/site-packages/moviepy/audio/AudioClip.py", line 209, in write_audiofile
      logger=logger)
    File "&lt;/usr/lib/python3.6/site-packages/decorator.py:decorator-gen-70&gt;", line 2, in ffmpeg_audiowrite
    File "/usr/lib/python3.6/site-packages/moviepy/decorators.py", line 54, in requires_duration
      return f(clip, *a, **k)
    File "/usr/lib/python3.6/site-packages/moviepy/audio/io/ffmpeg_audiowriter.py", line 169, in ffmpeg_audiowrite
      logger=logger):
    File "/usr/lib/python3.6/site-packages/moviepy/audio/AudioClip.py", line 85, in iter_chunks
      fps=fps, buffersize=chunksize)
    File "&lt;/usr/lib/python3.6/site-packages/decorator.py:decorator-gen-72&gt;", line 2, in to_soundarray
    File "/usr/lib/python3.6/site-packages/moviepy/decorators.py", line 54, in requires_duration
      return f(clip, *a, **k)
    File "/usr/lib/python3.6/site-packages/moviepy/audio/AudioClip.py", line 126, in to_soundarray
      snd_array = self.get_frame(tt)
    File "&lt;/usr/lib/python3.6/site-packages/decorator.py:decorator-gen-10&gt;", line 2, in get_frame
    File "/usr/lib/python3.6/site-packages/moviepy/decorators.py", line 89, in wrapper
      return f(*new_a, **new_kw)
    File "/usr/lib/python3.6/site-packages/moviepy/Clip.py", line 95, in get_frame
      return self.make_frame(t)
    File "/usr/lib/python3.6/site-packages/moviepy/audio/AudioClip.py", line 296, in make_frame
      for c, part in zip(self.clips, played_parts)
    File "/usr/lib/python3.6/site-packages/moviepy/audio/AudioClip.py", line 297, in &lt;listcomp&gt;
      if (part is not False)]
    File "&lt;/usr/lib/python3.6/site-packages/decorator.py:decorator-gen-10&gt;", line 2, in get_frame
    File "/usr/lib/python3.6/site-packages/moviepy/decorators.py", line 89, in wrapper
      return f(*new_a, **new_kw)
    File "/usr/lib/python3.6/site-packages/moviepy/Clip.py", line 95, in get_frame
      return self.make_frame(t)
    File "/usr/lib/python3.6/site-packages/moviepy/audio/io/AudioFileClip.py", line 78, in &lt;lambda&gt;
      self.make_frame = lambda t: self.reader.get_frame(t)
    File "/usr/lib/python3.6/site-packages/moviepy/audio/io/readers.py", line 184, in get_frame
      self.buffer_around(fr_max)
    File "/usr/lib/python3.6/site-packages/moviepy/audio/io/readers.py", line 238, in buffer_around
      array = self.read_chunk(chunksize)
    File "/usr/lib/python3.6/site-packages/moviepy/audio/io/readers.py", line 112, in read_chunk
      s = self.proc.stdout.read(L)
  AttributeError: 'NoneType' object has no attribute 'stdout'
  </code></pre>
  
  <p>Everything is correct and is working except for writing the CompositeVideoClip. How would I
  go about fixing this?</p>