Django - makemigrations - No changes detected
I solved that problem by doing this:

Erase the "db.sqlite3" file. The issue here is that your current data base will be erased, so you will have to remake it again.
Inside the migrations folder of your edited app, erase the last   updated file. Remember that the first created file is: "0001_initial.py". For example: I made a new class and register it by the "makemigrations" and "migrate" procedure, now a new file called "0002_auto_etc.py" was created; erase it.
Go to the "pycache" folder (inside the migrations folder) and erase the file "0002_auto_etc.pyc".
Finally, go to the console and use "python manage.py makemigrations" and "python manage.py migrate".
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?