Apply patch from Chris Lamb <lamby@debian.org> with minor revision.

Validate models before allowing connections via gunicorn_django

This prevents issues where the site is accepting connections but not all
of the models have loaded yet. If your model importing has side effects
(monkey-patching, etc) this can results in errors about missing attributes
or features simply because the code that enables those features as not been
run yet.

This issue does not affect the "run_gunicorn" management command as that
performs it's own model validation before allowing connections, so we are
simply making this consistent here.

Signed-off-by: Chris Lamb <lamby@debian.org>

gunicorn/app/djangoapp.py

@@ -69,12 +69,31 @@ class DjangoApplication(Application):
         sys.stderr.flush()
         sys.exit(1)
         
+    def validate(self):
+        """ Validate models. This also ensures that all models are 
+        imported in case of import-time side effects."""
+        from django.core.management.base import CommandError
+        from django.core.management.validation import get_validation_errors
+        try:
+            from cStringIO import StringIO
+        except ImportError:
+            from StringIO import StringIO
+
+        s = StringIO()
+        if get_validation_errors(s):
+            s.seek(0)
+            error = s.read()
+            sys.stderr.write("One or more models did not validate:\n%s" % error)
+            sys.stderr.flush()
+            sys.exit(1)
+
     def load(self):
         from django.conf import ENVIRONMENT_VARIABLE
         from django.core.handlers.wsgi import WSGIHandler
         os.environ[ENVIRONMENT_VARIABLE] = self.settings_modname
         # setup environ
         self.setup_environ()
+        self.validate()
         return WSGIHandler()
 
 class DjangoApplicationCommand(Application):