Django - makemigrations - No changes detected
My problem (and so solution) was yet different from those described above. 
I wasn't using models.py file, but created a models directory and created the my_model.py file there, where I put my model. Django couldn't find my model so it wrote that there are no migrations to apply. 
My solution was: in the my_app/models/__init__.py file I added this line:
from .my_model import MyModel
I was trying to create migrations within an existing app using the makemigrations command but it outputs "No changes detected".
Usually I create new apps using the startapp command but did not use it for this app when I created it.
After debugging, I found that it is not creating migration because the migrations package/folder is missing from an app. 
Would it be better if it creates the folder if it is not there or am I missing something?