Fix ImportError when providing a meaningless API version.

Ironicclient parses subcommand by API version. When providing a
meaningless (e.g 0.9) API version, the error message like 'No
module named v0.shell' is not humanized. This patch provides
the error more friendly.

Change-Id: I1d5130cde8fd60234523701b97b9d29f27380e93
Closes-Bug: #1654186

ironicclient/shell.py

@@ -19,6 +19,9 @@ from __future__ import print_function
 import argparse
 import getpass
 import logging
+import os
+import pkgutil
+import re
 import sys
 
 from keystoneauth1.loading import session as kasession
@@ -27,6 +30,7 @@ from oslo_utils import importutils
 import six
 
 import ironicclient
+from ironicclient.common.apiclient import exceptions
 from ironicclient.common import cliutils
 from ironicclient.common import http
 from ironicclient.common.i18n import _
@@ -235,14 +239,31 @@ class IronicShell(object):
 
         return parser
 
+    def get_available_major_versions(self):
+        matcher = re.compile(r"^v[0-9]+$")
+        submodules = pkgutil.iter_modules([os.path.dirname(__file__)])
+        available_versions = [name[1:] for loader, name, ispkg in submodules
+                              if matcher.search(name)]
+
+        return available_versions
+
     def get_subcommand_parser(self, version):
         parser = self.get_base_parser()
 
         self.subcommands = {}
         subparsers = parser.add_subparsers(metavar='<subcommand>',
                                            dest='subparser_name')
-        submodule = importutils.import_versioned_module('ironicclient',
+        try:
-                                                        version, 'shell')
+            submodule = importutils.import_versioned_module('ironicclient',
+                                                            version, 'shell')
+        except ImportError as e:
+            msg = _("Invalid client version '%(version)s'. "
+                    "Major part must be one of: '%(major)s'") % {
+                "version": version,
+                "major": ", ".join(self.get_available_major_versions())}
+            raise exceptions.UnsupportedVersion(
+                _('%(message)s, error was: %(error)s') %
+                {'message': msg, 'error': e})
         submodule.enhance_parser(parser, subparsers, self.subcommands)
         utils.define_commands_from_module(subparsers, self, self.subcommands)
         return parser

ironicclient/tests/unit/test_shell.py

@@ -24,6 +24,7 @@ import testtools
 from testtools import matchers
 
 from ironicclient import client
+from ironicclient.common.apiclient import exceptions
 from ironicclient.common import http
 from ironicclient import exc
 from ironicclient import shell as ironic_shell
@@ -251,6 +252,10 @@ class ShellTest(utils.BaseTestCase):
         self.assertRaises(exc.CommandError,
                           self.shell, '--ironic-api-version 1.2.1 help')
 
+    def test_invalid_ironic_api_version(self):
+        self.assertRaises(exceptions.UnsupportedVersion,
+                          self.shell, '--ironic-api-version 0.8 help')
+
 
 class TestCase(testtools.TestCase):