Use string.ascii_letters to be python 3 compatible

Use string.ascii_letters instead of string.letter. The only consequence
is to loose the locale-specific behavior but it seems not to be a bad
thing for generating a secret key.

Change-Id: Id985d798042eaa7541692d137027233537ed3bb4
Closes-Bug: #1360861
Add columns to the job executions page

Add 'Job' and 'Cluster' columns to job executions page
to make it more useful.

Closes-Bug: #1342293

Change-Id: I2c8d9802e1199127f997df1259770e5d84bff8cf
Remove #noqa from two common imports and add them to import_exceptions

We have two imports with #noqa: django.conf.urls.patterns and
django.conf.urls.url however using them is a standard way of creating
any urls.py module. So there are over 150 imports in Horizon code
where #noqa could be replaced with two lines in list of import_exceptions.

Change-Id: I81c3290e0dc958b5037dd6a87e44df18adfbe751
Updated from global requirements

Change-Id: Ic109848be099e382e2f946bf2b3b0bcc0b055049
Merge "Use string.ascii_letters to be python 3 compatible"
Merge "Add columns to the job executions page"
Merge "Updated from global requirements"
Merge "Remove #noqa from two common imports and add them to import_exceptions"