Fixed #18387 -- Do not call sys.exit during call_command.

Moved sys.exit(1) so as failing management commands reach it
only when running from command line.

tests/modeltests/user_commands/management/commands/dance.py

@@ -1,6 +1,6 @@
 from optparse import make_option
 
-from django.core.management.base import BaseCommand
+from django.core.management.base import BaseCommand, CommandError
 
 
 class Command(BaseCommand):
@@ -8,11 +8,13 @@ class Command(BaseCommand):
     args = ''
     requires_model_validation = True
 
-    option_list =[
+    option_list = BaseCommand.option_list + (
         make_option("-s", "--style", default="Rock'n'Roll"),
         make_option("-x", "--example")
-    ]
+    )
 
     def handle(self, *args, **options):
         example = options["example"]
+        if example == "raise":
+            raise CommandError()
         self.stdout.write("I don't feel like dancing %s." % options["style"])