Raise a CommandError instead of printing a message

If an AnVILAPIError is raised by the command, re-raise a CommandError
instead of printing an error and exiting normally. This should give
the proper return code when the command is run, which means that
cron jobs encountering errors should email us.

anvil_consortium_manager/management/commands/run_anvil_audit.py

@@ -3,7 +3,7 @@
 import django_tables2 as tables
 from django.contrib.sites.models import Site
 from django.core.mail import send_mail
-from django.core.management.base import BaseCommand
+from django.core.management.base import BaseCommand, CommandError
 from django.template.loader import render_to_string
 
 from ...anvil_api import AnVILAPIError
@@ -58,7 +58,7 @@ def _run_audit(self, audit_results, **options):
             # Assume the method is called anvil_audit.
             audit_results.run_audit()
         except AnVILAPIError:
-            self.stdout.write(self.style.ERROR("API error."))
+            raise CommandError("API error.")
         else:
             if not audit_results.ok():
                 self.stdout.write(self.style.ERROR("problems found."))

anvil_consortium_manager/tests/test_commands.py

@@ -254,8 +254,8 @@ def test_command_run_audit_api_error(self):
         api_url = self.get_api_url_billing_project(billing_project.name)
         self.anvil_response_mock.add(responses.GET, api_url, status=500, json={"message": "error"})
         out = StringIO()
-        call_command("run_anvil_audit", "--no-color", models=["BillingProject"], stdout=out)
-        self.assertIn("BillingProjectAudit... API error.", out.getvalue())
+        with self.assertRaises(CommandError):
+            call_command("run_anvil_audit", "--no-color", models=["BillingProject"], stdout=out)
 
     # This test is complicated so skipping for now.
     # When trying to change the settings, the test attempts to repopulate the