Django Compressor: multiple errors when ran but working fine

Question

I have installed django-compressor==2.4.1 on my Django==2.2.28 project.

As on the documentation, I installed it by putting compressor in my INSTALLED_APPS and added 'compressor.finders.CompressorFinder' to my STATICFILES_FINDERS.

by now I am just trying it and using it on my base.html on the following:

        {% compress css %}
            <link rel="stylesheet" type="text/css" href="{% static 'css/survey.css' %}"/>
            <link rel="stylesheet" type="text/css" href="{% static 'css/bootstrap.min.css' %}"/>
            <link rel="stylesheet" type="text/css" href="{% static 'css/Roboto.css' %}">
            <link rel="stylesheet" type="text/css" href="{% static 'css/AdminLTE.min.css' %}">
            <link rel="stylesheet" type="text/css" href="{% static 'css/jquery.dataTables.min.css' %}"/>
            <link rel="stylesheet" type="text/css" href="{% static 'css/index.css' %}"/>
        {% endcompress %}

And I enabled the following settings:

# Django Compressor
COMPRESS_ENABLED = True
COMPRESS_OFFLINE = True
COMPRESS_OFFLINE_TIMEOUT = 31536000  # 1 year in seconds

but when I run manage.py compress the console is filled with errors, all about files that seem to be in the very same django-compressor folder. The compressed file gets made anyway and everything works fine.

Here is the full output: https://pastebin.com/20kuHKLw

Can anyone explain what is happening?