Django: loaddata in migrations errors
When you run python manage.py migrate it's trying to load your testmodel.json in fixtures folder, but your model (after updated) does not match with data in testmodel.json. You could try this: 

Change your directory from fixture to _fixture.
Run python manage.py migrate
Optional, you now can change _fixture by fixture and load your data as before with migrate command or load data with python manage.py loaddata app/_fixtures/testmodel.json
Something really annoying is happening to me since using Django migrations (not south) and using loaddata for fixtures inside of them.
Here is a simple way to reproduce my problem:

create a new model Testmodel with 1 field field1 (CharField or whatever)
create an associated migration (let's say 0001) with makemigrations
run the migration
and add some data in the new table
dump the data in a fixture testmodel.json
create a migration with call_command('loaddata', 'testmodel.json'): migration 0002
add some a new field to the model: field2
create an associated migration (0003)

Now, commit that, and put your db in the state just before the changes: ./manage.py migrate myapp zero. So you are in the same state as your teammate that didn't get your changes yet.
If you try to run ./manage.py migrate again you will get a ProgrammingError at migration 0002 saying that "column field2 does not exist".
It seems it's because loaddata is looking into your model (which is already having field2), and not just applying the fixture to the db.
This can happen in multiple cases when working in a team, and also making the test runner fail.
Did I get something wrong? Is it a bug? What should be done is those cases?
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I am using django 1.7