AdminUtils: Skip unsupported resources

Some admin util resources depends on external libreries that are not
always installed.
This patch will skip those, so the rest of the resources can be used.

Change-Id: I860f054fdadfe9ced93c3ba77f9b5d82b07da9fa

vmware_nsx/shell/resources.py

@@ -291,10 +291,34 @@ cli_opts = [cfg.StrOpt('fmt',
             ]
 
 
+# Describe dependencies between admin utils resources and external libraries
+# that are not always installed
+resources_dependencies = {
+    'nsxv': {'gw_edges': ['neutron_dynamic_routing.extensions']}}
+
+
+def verify_external_dependencies(plugin_name, resource):
+    if plugin_name in resources_dependencies:
+        deps = resources_dependencies[plugin_name]
+        if resource in deps:
+            for d in deps[resource]:
+                try:
+                    importlib.import_module(d)
+                except ImportError:
+                    return False
+    return True
+
+
 def init_resource_plugin(plugin_name, plugin_dir):
     plugin_resources = get_resources(plugin_dir)
     for resource in plugin_resources:
         if (resource != '__init__'):
+            # skip unsupported resources
+            if not verify_external_dependencies(plugin_name, resource):
+                LOG.info("Skipping resource %s because of dependencies",
+                         resource)
+                continue
+            # load the resource
             importlib.import_module(
                 "vmware_nsx.shell.admin.plugins."
                 "{}.resources.".format(plugin_name) + resource)