custom font not working in Python

[Sokhavuth]

I want to use custom fonts in my Python app. It works like a charm on my local machine. However, when I push to Space, it is not working by showing the error as below:

[ERROR] UnicodeDecodeError: 'utf-8' codec can't decode byte 0xf6 in position 18: invalid start byte
Traceback (most recent call last):
  File "/opt/python/detalib/debugger.py", line 131, in wrap
    return func(event, context)
  File "/var/task/_entry.py", line 15, in handler
    return handle(event, main)
  File "/opt/python/detalib/handler.py", line 32, in handle
    return handlers.handle_bare_wsgi(event, main, context)
  File "/opt/python/detalib/handlers.py", line 32, in handle_bare_wsgi
    return resolve(main.app, event)
  File "/opt/python/detalib/adapters/wsgi/__init__.py", line 151, in resolve
    return response.as_apig_response()
  File "/opt/python/detalib/adapters/wsgi/__init__.py", line 117, in as_apig_response
    response["body"] = self.body.getvalue().decode("utf-8")[ERROR] UnicodeDecodeError: 'utf-8' codec can't decode byte 0x80 in position 7: invalid start byte
Traceback (most recent call last):
  File "/opt/python/detalib/debugger.py", line 131, in wrap
    return func(event, context)
  File "/var/task/_entry.py", line 15, in handler
    return handle(event, main)
  File "/opt/python/detalib/handler.py", line 32, in handle
    return handlers.handle_bare_wsgi(event, main, context)
  File "/opt/python/detalib/handlers.py", line 32, in handle_bare_wsgi
    return resolve(main.app, event)
  File "/opt/python/detalib/adapters/wsgi/__init__.py", line 151, in resolve
    return response.as_apig_response()
  File "/opt/python/detalib/adapters/wsgi/__init__.py", line 117, in as_apig_response
    response["body"] = self.body.getvalue().decode("utf-8")

Any help would be very thankful.