Django migration dependencies reference nonexistent parent node

I have a problem with django migrations. I get this error:

django.db.migrations.exceptions.NodeNotFoundError: Migration user.0050_merge_20170523_1254 dependencies reference nonexistent parent node ('user', '0049_auto_20170519_1934')

I fix the errors, deleting some lines but after I fix all these errors, I get another:

ValueError: Could not find common ancestor of {'0050_merge_20170523_1254', '0007_auto_20170524_1540'}

I can't solve that. I can drop database and do makemigrations again... but in production environment, I'd want to know how to fix this correctly, without drop database haha.

Thanks!

Next time when you rollback:

1. Go into the migrations folder in your app.
2. Look for the migration file where you would like to go back to. (for example "0012_post_category.py")
3. go in the terminal write: ./manage.py migrate yourAppName 0012 (this is just the example number) and hit enter
4. if everything goes well. Delete the other migrations which came after this number in your migrations folder.

Do not just delete migrations! Hope that helps.