Use build_app from app.py, not from wsgi.py

For tests it's important to use `build_app` from app.py because it doesn't
use the `HTTPLoggerMiddleware`. This makes us possible to run tests without
write permissions in `/var/log/nailgun`.

The commit also removes the obsolete `paste` package from dependencies.

Change-Id: I401ef74abc95961d5687d12835752b881ef0e7ef
Closes-Bug: #1396685

nailgun/nailgun/test/integration/test_db_refresh.py

@@ -17,14 +17,14 @@
 from datetime import datetime
 from unittest import TestCase
 
-from paste.fixture import TestApp
 from sqlalchemy import orm
+from webtest.app import TestApp
 
+from nailgun.app import build_app
 from nailgun.db import engine
 from nailgun.db import flush
 from nailgun.db import NoCacheQuery
 from nailgun.db.sqlalchemy.models import Node
-from nailgun.wsgi import build_app
 
 
 class TestDBRefresh(TestCase):

nailgun/requirements.txt

@@ -2,7 +2,6 @@ Babel==1.3
 Jinja2==2.7
 Mako==0.9.1
 MarkupSafe==0.18
-Paste==1.7.5.1
 PyYAML==3.10
 SQLAlchemy>=0.9.4
 alembic>=0.6.2