Unify error messages

Unify error messages for CLI

Unify error messages for hub

Fixes: https://pagure.io/koji/issue/2720

tests/test_cli/test_add_pkg.py

@@ -1,11 +1,11 @@
 from __future__ import absolute_import
 
-import mock
 import os
-import six
 import sys
 import unittest
 
+import mock
+import six
 from mock import call
 
 from koji_cli.commands import handle_add_pkg
@@ -133,7 +133,7 @@ class TestAddPkg(utils.CliTestCase):
             handle_add_pkg(options, session, args)
         self.assertExitCode(ex, 1)
         actual = stderr.getvalue()
-        expected = 'User owner does not exist\n'
+        expected = 'No such user: %s\n' % owner
         self.assertMultiLineEqual(actual, expected)
         # Finally, assert that things were called as we expected.
         activate_session_mock.assert_not_called()
@@ -168,7 +168,7 @@ class TestAddPkg(utils.CliTestCase):
             handle_add_pkg(options, session, args)
         self.assertExitCode(ex, 1)
         actual = stdout.getvalue()
-        expected = 'No such tag: tag\n'
+        expected = 'No such tag: %s\n' % tag
         self.assertMultiLineEqual(actual, expected)
         # Finally, assert that things were called as we expected.
         activate_session_mock.assert_called_once_with(session, options)