Fixes the Python 3 dependencies and iterator

A. Fixes depedencies of Python 3:

Following the documentation about Python 3 requirements.
It was needed to change in the file ./requirements.txt
replacing "python-openid" with "python3-openid".

B. Fixing Python 3 compatibility in the migration script:

In order to fix the migration script to run on Python 3
I changed the line #24 on ./migrate/launchpad/reader.py,
changing the iterator.

Also, I added  in the file "./requirements.txt" a comment
to use the library "launchpadlib" in order to run
the migrate script.

Change-Id: Iedcd283ade1ea62fdc5777dfe7b1ae5916db3480

requirements.txt

@@ -11,7 +11,7 @@ pecan>=0.4.5
 oslo.db>=4.27.0  # Apache-2.0
 oslo.log>=1.0.0
 pika>=0.9.14
-python-openid
+python3-openid
 PyYAML>=3.1.0
 requests>=1.1
 six>=1.7.0
@@ -28,3 +28,4 @@ apscheduler>=3.0.1,<3.1.0
 python_dateutil>=2.4.0
 oslo.concurrency>=3.8.0         # Apache-2.0
 oslo.i18n>=2.1.0  # Apache-2.0
+#launchpadlib         # Only for migration

storyboard/migrate/launchpad/reader.py

@@ -39,4 +39,4 @@ class LaunchpadReader(object):
         return self.next()
 
     def next(self):
-        return self.task_iterator.next()
+        return next(self.task_iterator)