migrate --check still emits signals if database is up to date

[Jacob Walls]

pre_migrate and post_migrate signals are emitted for migrate --check, but only if the database is up-to-date.

A related side effect is that the logs also look like a like a real run, as it says "Operations to perform:" and "Running migrations:". The last sentence clarifies that nothing has been applied, but there is still the potential for a half-second of "what have I just done?".

% python manage.py migrate --check          
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sessions, social_django
Running migrations:
  No migrations to apply.

I think the patch is as simple as:

diff --git a/django/core/management/commands/migrate.py b/django/core/management/commands/migrate.py
index d98072c66e..f1b8a21c11 100644
--- a/django/core/management/commands/migrate.py
+++ b/django/core/management/commands/migrate.py
@@ -237,7 +237,7 @@ class Command(BaseCommand):
                     self.stdout.write("  No migrations to prune.")
 
         plan = executor.migration_plan(targets)
-        exit_dry = plan and options["check_unapplied"]
+        exit_dry = options["check_unapplied"]
 
         if options["plan"]:
             self.stdout.write("Planned operations:", self.style.MIGRATE_LABEL)