Creates the tag with project name and priority

This patch adds to the migration script the feature
to use the priority field from "Launchpad task" to
create a tag to the "Storyboard's Story". So, this
tag will be prefixed with the project and followed
by the task priority.

Ex: project_name-priority, manila-high

Change-Id: I6664a9ca0cdb9fbe265e0f18ab3ae8f879475466
Task: 28146

storyboard/migrate/launchpad/writer.py

@@ -66,6 +66,11 @@ class LaunchpadWriter(object):
                   one first." % (project_name))
             sys.exit(1)
 
+    def build_priority_tag(self, priority):
+        """Writes in the tag, the project name, and your priority."""
+        priority_tag = '{}-{}'.format(self.project.name, priority)
+        return self.build_tag(priority_tag)
+
     def write_tags(self, bug):
         """Extracts the tags from a launchpad bug, seeds/loads them in the
         StoryBoard database, and returns a list of the corresponding entities.
@@ -227,6 +232,9 @@ class LaunchpadWriter(object):
             title = title[:97] + '...'
             description = bug.title + '\n\n' + description
 
+        # Create priority tag
+        tags.append(self.build_priority_tag(priority))
+
         # Sanity check.
         story = {
             'id': launchpad_id,