Show full path of `local_manifests` folder in deprecation warning

When a local_manifest.xml file is present, a deprecation warning
is printed telling the user to put local manifest files in the
`local_manifests` directory.

Include the full path to the `local_manifests` directory in the
warning, to reduce confusion about where the directory should be
located.  Also enclose the directory name in backticks.

Change-Id: I85710cfbd6e77fb2fa6b7b0ce66d77693ccd649f

manifest_xml.py

@@ -335,8 +335,8 @@ class XmlManifest(object):
 
       local = os.path.join(self.repodir, LOCAL_MANIFEST_NAME)
       if os.path.exists(local):
-        print('warning: %s is deprecated; put local manifests in %s instead'
-              % (LOCAL_MANIFEST_NAME, LOCAL_MANIFESTS_DIR_NAME),
+        print('warning: %s is deprecated; put local manifests in `%s` instead'
+              % (LOCAL_MANIFEST_NAME, os.path.join(self.repodir, LOCAL_MANIFESTS_DIR_NAME)),
               file=sys.stderr)
         nodes.append(self._ParseManifestXml(local, self.repodir))