Use .display_name instead of metadata['display_name']

* the former does a fallback if metadata['display_name'] isn't set.

common/lib/xmodule/xmodule/capa_module.py

@@ -237,7 +237,7 @@ class CapaModule(XModule):
             else:
                 raise
 
-        content = {'name': self.metadata['display_name'],
+        content = {'name': self.display_name,
                    'html': html,
                    'weight': self.weight,
                    }

common/lib/xmodule/xmodule/course_module.py

@@ -140,7 +140,7 @@ class CourseDescriptor(SequenceDescriptor):
 
     @property
     def title(self):
-        return self.metadata['display_name']
+        return self.display_name
 
     @property
     def number(self):

common/lib/xmodule/xmodule/seq_module.py

@@ -76,7 +76,7 @@ class SequenceModule(XModule):
             contents.append({
                 'content': child.get_html(),
                 'title': "\n".join(
-                    grand_child.metadata['display_name'].strip()
+                    grand_child.display_name.strip()
                     for grand_child in child.get_children()
                     if 'display_name'  in grand_child.metadata
                 ),

lms/djangoapps/lms_migration/migrate.py

@@ -77,7 +77,7 @@ def manage_modulestores(request,reload_dir=None):
 
     for cdir, course in def_ms.courses.items():
         html += '<hr width="100%"/>'
-        html += '<h2>Course: %s (%s)</h2>' % (course.metadata['display_name'],cdir)
+        html += '<h2>Course: %s (%s)</h2>' % (course.display_name,cdir)
 
         for field in dumpfields:
             data = getattr(course,field)