Remove unused variables (flake8 F841)

Change-Id: I716a6b61c2b3faaa23cc79f58c6c6e01cfc232f2
Migrate to pbr.

Closes bug 1179007

Change-Id: I9d2a0190bb8dc31ea481909a4e0af3008aa976bf
Merge "Migrate to pbr."
Merge "Remove unused variables (flake8 F841)"
Enumerate ignored flake8 H* rules

We were previously ignoring all H* rules; this patch specifically
identifies them so that we can eliminate them one by one, without
introducing regressions along the way.

Change-Id: I3f18f8f9aec8657697c711f5fbb23ec687ce28f0
Remove unnecessary commented out code

This commit removes unnecessary commented out code in
keystone/identity/backends/ldap/core.py. This change introduces no
functional change

Change-Id: Ia84d59c0e336a80d11821b11788d36cdb36032c4
Use TODO(NAME) (flake8 H101)

Change-Id: Ic47bdd61d9818f203a88ae16f97c2b61b1c1bd8c
use the 'not in' operator (flake8 H902)

... when evaluating membership in a collection.

Change-Id: I3fd3d5b5d5ea505833be50193b8969f8c4feb135
consistent i18n placeholders (flake8 H701, H702, H703)

- eliminates ambiguously defined keywords in i18n strings which may
  become incorrectly ordered in a corresponding translation.
- ensures formatting operations occur outside of i18n calls
- use bare multiline string concatenation instead of 'ab' + \n 'cd'
- eliminates an 'empty localization string' (passing a variable to i18n
  function)

Change-Id: I0d78b978cc730e5fb892b80dfacaaf6687cd80be
eliminate 'except:' (flake8 H201)

Change-Id: Ic53b43b96c490557352be212ac79a7e8a249c21a
one import per line (flake8 H301)

Change-Id: Idb93169a0b64861bff22d06304c020865dd0a0ab
Merge "Remove unnecessary commented out code"
import only modules (flake8 H302)

Change-Id: I0fa6fc6bf9d51b60fa987a0040168f3f0ef78a4a