Improve import related error handling

If there was a problem importing a library we would incorrectly raise
an unsupported version error:

  $ glance --os-image-api-version 1 image-list
  "1" is not a supported API version. Example values are "1" or "2".

We should change this to provide information on the failed import, eg:

  $ glance --os-image-api-version 1 image-list
  No module named badimport

We also now raise the full stacktrace in this case if '--debug' is passed
on the command line.

Change-Id: I1c687ae6c5da239090b0b7a4a855b3271a9076da
Related-bug: 1402632

glanceclient/shell.py

@@ -47,6 +47,8 @@ from keystoneclient import session
 osprofiler_profiler = importutils.try_import("osprofiler.profiler")
 _ = _i18n._
 
+SUPPORTED_VERSIONS = [1, 2]
+
 
 class OpenStackImagesShell(object):
 
@@ -291,12 +293,7 @@ class OpenStackImagesShell(object):
 
         self.subcommands = {}
         subparsers = parser.add_subparsers(metavar='<subcommand>')
-        try:
+        submodule = utils.import_versioned_module(version, 'shell')
-            submodule = utils.import_versioned_module(version, 'shell')
-        except ImportError:
-            print('"%s" is not a supported API version. Example '
-                  'values are "1" or "2".' % version)
-            utils.exit()
 
         self._find_actions(subparsers, submodule)
         self._find_actions(subparsers, self)
@@ -602,14 +599,32 @@ class OpenStackImagesShell(object):
         # build available subcommands based on version
         try:
             api_version = int(options.os_image_api_version or url_version or 1)
+            if api_version not in SUPPORTED_VERSIONS:
+                raise ValueError
         except ValueError:
-            print("Invalid API version parameter")
+            msg = ("Invalid API version parameter. "
-            utils.exit()
+                   "Supported values are %s" % SUPPORTED_VERSIONS)
+            utils.exit(msg=msg)
 
         if api_version == 2:
             self._cache_schemas(options)
 
-        subcommand_parser = self.get_subcommand_parser(api_version)
+        try:
+            subcommand_parser = self.get_subcommand_parser(api_version)
+        except ImportError as e:
+            if options.debug:
+                traceback.print_exc()
+            if not str(e):
+                # Add a generic import error message if the raised ImportError
+                # has none.
+                raise ImportError('Unable to import module. Re-run '
+                                  'with --debug for more info.')
+            raise
+        except Exception:
+            if options.debug:
+                traceback.print_exc()
+            raise
+
         self.parser = subcommand_parser
 
         # Handle top-level --help/-h before attempting to parse

glanceclient/tests/unit/test_shell.py

@@ -27,10 +27,11 @@ import requests
 from requests_mock.contrib import fixture as rm_fixture
 import six
 
+from glanceclient.common import utils
 from glanceclient import exc
 from glanceclient import shell as openstack_shell
+from glanceclient.tests import utils as testutils
 
-from glanceclient.tests import utils
 #NOTE (esheffield) Used for the schema caching tests
 from glanceclient.v2 import schemas as schemas
 import json
@@ -75,7 +76,7 @@ _s = V3_TOKEN.add_service('image', name='glance')
 _s.add_standard_endpoints(public=DEFAULT_IMAGE_URL)
 
 
-class ShellTest(utils.TestCase):
+class ShellTest(testutils.TestCase):
     # auth environment to use
     auth_env = FAKE_V2_ENV.copy()
     # expected auth plugin to invoke
@@ -311,6 +312,58 @@ class ShellTest(utils.TestCase):
         except SystemExit as ex:
             self.assertEqual(130, ex.code)
 
+    @mock.patch('glanceclient.common.utils.exit', side_effect=utils.exit)
+    def test_shell_illegal_version(self, mock_exit):
+        # Only int versions are allowed on cli
+        shell = openstack_shell.OpenStackImagesShell()
+        argstr = '--os-image-api-version 1.1 image-list'
+        try:
+            shell.main(argstr.split())
+        except SystemExit as ex:
+            self.assertEqual(1, ex.code)
+        msg = ("Invalid API version parameter. "
+               "Supported values are %s" % openstack_shell.SUPPORTED_VERSIONS)
+        mock_exit.assert_called_with(msg=msg)
+
+    @mock.patch('glanceclient.common.utils.exit', side_effect=utils.exit)
+    def test_shell_unsupported_version(self, mock_exit):
+        # Test an integer version which is not supported (-1)
+        shell = openstack_shell.OpenStackImagesShell()
+        argstr = '--os-image-api-version -1 image-list'
+        try:
+            shell.main(argstr.split())
+        except SystemExit as ex:
+            self.assertEqual(1, ex.code)
+        msg = ("Invalid API version parameter. "
+               "Supported values are %s" % openstack_shell.SUPPORTED_VERSIONS)
+        mock_exit.assert_called_with(msg=msg)
+
+    @mock.patch.object(openstack_shell.OpenStackImagesShell,
+                       'get_subcommand_parser')
+    def test_shell_import_error_with_mesage(self, mock_parser):
+        msg = 'Unable to import module xxx'
+        mock_parser.side_effect = ImportError('%s' % msg)
+        shell = openstack_shell.OpenStackImagesShell()
+        argstr = '--os-image-api-version 2 image-list'
+        try:
+            shell.main(argstr.split())
+            self.fail('No import error returned')
+        except ImportError as e:
+            self.assertEqual(msg, str(e))
+
+    @mock.patch.object(openstack_shell.OpenStackImagesShell,
+                       'get_subcommand_parser')
+    def test_shell_import_error_default_message(self, mock_parser):
+        mock_parser.side_effect = ImportError
+        shell = openstack_shell.OpenStackImagesShell()
+        argstr = '--os-image-api-version 2 image-list'
+        try:
+            shell.main(argstr.split())
+            self.fail('No import error returned')
+        except ImportError as e:
+            msg = 'Unable to import module. Re-run with --debug for more info.'
+            self.assertEqual(msg, str(e))
+
     @mock.patch('glanceclient.v1.client.Client')
     def test_auth_plugin_invocation_without_username_with_v1(self, v1_client):
         self.make_env(exclude='OS_USERNAME')
@@ -419,7 +472,7 @@ class ShellTestWithKeystoneV3Auth(ShellTest):
             self.assertNotIn(r, stdout.split())
 
 
-class ShellCacheSchemaTest(utils.TestCase):
+class ShellCacheSchemaTest(testutils.TestCase):
     def setUp(self):
         super(ShellCacheSchemaTest, self).setUp()
         self._mock_client_setup()