increase test coverage for drf_create_token command

tests/test_authtoken.py

@@ -1,7 +1,7 @@
 import pytest
 from django.contrib.admin import site
 from django.contrib.auth.models import User
-from django.core.management import call_command
+from django.core.management import call_command, CommandError
 from django.test import TestCase
 from django.utils.six import StringIO
 
@@ -71,6 +71,11 @@ def test_command_do_not_reset_user_token(self):
 
         assert first_token_key == second_token_key
 
+    def test_command_raising_error_for_invalid_user(self):
+        out = StringIO()
+        with pytest.raises(CommandError):
+            call_command('drf_create_token', 'not_existing_user', stdout=out)
+
     def test_command_output(self):
         out = StringIO()
         call_command('drf_create_token', self.user.username, stdout=out)