Make failures of image-builder more human-friendly

Change-Id: I34fd36220b9be3fee0cd08901599ce3f5bdc2116

shaker/engine/image_builder.py

@@ -34,10 +34,18 @@ def init():
     utils.init_config_and_logging(
         config.OPENSTACK_OPTS + config.IMAGE_BUILDER_OPTS)
 
-    openstack_client = openstack.OpenStackClient(
-        username=cfg.CONF.os_username, password=cfg.CONF.os_password,
-        tenant_name=cfg.CONF.os_tenant_name, auth_url=cfg.CONF.os_auth_url,
-        region_name=cfg.CONF.os_region_name)
+    openstack_client = None
+    try:
+        openstack_client = openstack.OpenStackClient(
+            username=cfg.CONF.os_username, password=cfg.CONF.os_password,
+            tenant_name=cfg.CONF.os_tenant_name, auth_url=cfg.CONF.os_auth_url,
+            region_name=cfg.CONF.os_region_name)
+    except Exception as e:
+        LOG.error('Error establishing connection to OpenStack: %s. '
+                  'Please verify OpenStack credentials (--os-username, '
+                  '--os-password, --os-tenant-name, --os-auth-url)', e)
+        exit(1)
+
     return openstack_client
 
 
@@ -56,13 +64,23 @@ def build_image():
     if glance.get_image(openstack_client.glance, image_name):
         LOG.info('Using existing image: %s', image_name)
     else:
+        template = None
+        template_filename = cfg.CONF.image_builder_template
+        try:
+            template = utils.read_file(template_filename)
+        except IOError:
+            LOG.error('Error reading template file: %s. '
+                      'Please verify correctness of --image-builder-template '
+                      'parameter', template_filename)
+            exit(1)
+
         external_net = (cfg.CONF.external_net or
                         neutron.choose_external_net(openstack_client.neutron))
         stack_params = {
             'stack_name': 'shaker_%s' % uuid.uuid4(),
             'parameters': {'external_net': external_net,
                            'flavor': flavor_name},
-            'template': utils.read_file(cfg.CONF.image_builder_template),
+            'template': template,
         }
 
         stack = openstack_client.heat.stacks.create(**stack_params)['stack']

shaker/engine/utils.py

@@ -70,6 +70,16 @@ def init_config_and_logging(opts):
 
 def read_file(file_name, base_dir=''):
     full_path = os.path.normpath(os.path.join(base_dir, file_name))
+    if not os.path.exists(full_path):
+        # treat file_name as relative to shaker's package root
+        full_path = os.path.normpath(os.path.join(
+            os.path.dirname(__import__('shaker').__file__), '../', file_name))
+        if not os.path.exists(full_path):
+            msg = ('File %s not found by absolute nor by relative path' %
+                   file_name)
+            LOG.error(msg)
+            raise IOError(msg)
+
     fd = None
     try:
         fd = open(full_path)