Merge pull request #1289 from MITx/bugfix/dave/dont_explode_askbot_migration

Add a try/catch so that Askbot removal doesn't die if there's no Askbot ...

common/djangoapps/student/migrations/0021_remove_askbot.py

@@ -26,6 +26,7 @@ class Migration(SchemaMigration):
 
     def forwards(self, orm):
         "Kill the askbot"
+        try:
             # For MySQL, we're batching the alters together for performance reasons
             if db.backend_name == 'mysql':
                 drops = ["drop `{0}`".format(col) for col in ASKBOT_AUTH_USER_COLUMNS]
@@ -34,6 +35,8 @@ class Migration(SchemaMigration):
             else:
                 for column in ASKBOT_AUTH_USER_COLUMNS:
                     db.delete_column('auth_user', column)
+        except Exception as ex:
+            print "Couldn't remove askbot because of {0} -- it was probably never here to begin with.".format(ex)            
 
     def backwards(self, orm):
         raise RuntimeError("Cannot reverse this migration: there's no going back to Askbot.")