First of all, you need to add other_module to your Docker image. Without that, the pip install command will not be able to find it. However you cant ADD a directory that is outside the directory of the Dockerfile according to the documentation:
The path must be inside the context of the build; you cannot ADD
../something /something, because the first step of a docker build is
to send the context directory (and subdirectories) to the docker
daemon.
So you have to move the other_module directory into the same directory as your Dockerfile, i.e. your structure should look something like
.
├── Dockerfile
├── requirements.txt
├── other_module
| ├── modue_file.xyz
| └── another_module_file.xyz
then add the following to the dockerfile:
ADD /other_module /other_module
ADD requirements.txt /app
WORKDIR /app
RUN pip install -r requirements.txt
The WORKDIR command moves you into /app so the next step, RUN pip install... will be executed inside the /app directory. And from the app-directory, you now have the directory../other_module avaliable