Increased test coverage of django.db.migrations.questioner.

[jacobtylerwalls]

Only uncovered line now is this return False for ambiguous namespace packages:

django/django/db/migrations/questioner.py

Lines 51 to 52 in b0d16d0

	if len(migrations_module.__path__) > 1:
	return False

[felixxm]

@jacobtylerwalls Thanks 👍 I made small edits.