I can't concadenate mkv clips on Ubuntu 20.04 with MoviePy

I'm on a Docker container with Ubuntu 20.04 and I want to concadenate a set of videoclips from a mkv file with MoviePy

This is my code:

combinated_video = concatenate_videoclips(clips)video_name, extension = os.path.splitext(self.video_path)combinated_video_path = video_name +"_combinated" + extensioncombinated_video.write_videofile(combinated_video_path, codec="libx264", audio_codec="mp3")

clips is a list like this:

[<moviepy.video.io.VideoFileClip.VideoFileClip object at 0x7f07eff86400>, <moviepy.video.io.VideoFileClip.VideoFileClip object at 0x7f07eff86670>, <moviepy.video.io.VideoFileClip.VideoFileClip object at 0x7f07eff86940>, <moviepy.video.io.VideoFileClip.VideoFileClip object at 0x7f07eff86c10>, <moviepy.video.io.VideoFileClip.VideoFileClip object at 0x7f07eff86100>]

I tried it on my local machine with Windows 11 and it worked, but it doesn't on Ubuntu 20.04

This is the error i get:

MoviePy couldn't find the codec associated with the filename. Provide the 'codec' parameter in write_videofile.

This is the Dockerfile used:

# syntax=docker/dockerfile:1FROM nvidia/cuda:11.3.1-cudnn8-devel-ubuntu20.04ENV TZ=Europe/MadridRUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezoneRUN apt-get update && apt-get upgrade -yRUN apt-get install -y \    python3.8 \    python3-pip \    python3-dev \    ffmpeg \    libsm6 \    libxext6RUN echo 'alias [python](https://saturncloud.io/glossary/python)="python3" '>> ~/.bashrcRUN echo 'alias pip="pip3" '>> ~/.bashrcWORKDIR /appCOPY requirements.txt .COPY app.py .RUN pip install --no-cache-dir -r requirements.txtEXPOSE 5555CMD ["python3", "app.py"]