manage.py startapp creates read-only files from within docker
You are probably running your container as root user. Hence you do not have the permission to edit them via your editor.
Try running your container with a regular user (for example docker run  --user 1000:1000 whatever-you-need).
I have a django app running in a docker container. I bashed into the container and used python manage.py startapp. However, the created directories and files appear to be read-only. From within intellij, I am unable to edit the files. I get a popup offering to clear the readonly status, but that just gives me an error unable to clear readonly status on the following files. 
How can I edit my files outside of the container?