Sync several modules from oslo-incubator

This change syncronizes excutils,lockutils,log, and
db.sqlalchemy.session modules from oslo-incubator
commit 19e0a51204df247dc38de880d08e6d66e89e6572 .

 $ python update.py --nodeps --base keystone --dest-dir ../keystone \
     --modules  excutils,lockutils,log,db.sqlalchemy.session

This includes fixes for 2 problems:

"keystone=INFO" was in the default_log_levels. This made it
more difficult than necessary to debug the Keystone server,
since you can set debug=True but then the keystone logging
level is overridden and you get no debug output for keystone.

"keystone=INFO" may have been in the default_log_levels because
of the auth_token middleware, but this has been moved to
python-keystoneclient now and the logging config for the
python APIs is done differently.

Closes-Bug: 1245629

Also, fixes some warnings and errors when docs are generated.

Change-Id: I53868bef975f73b4aee35695b6387b718c4179f9
Sync with global requirements

Change-Id: Ibdd73aa142be103d285ce0f15701dc96c1ec34ae
remove unused LOG

Change-Id: I5dec1b23667c7226697f064fe793c556c71e3abe
Use six.string_types instead of basestring

basestring only exists in Python 2. Use six.string_types to make code
Python 3 compatible. See http://pythonhosted.org/six/#six.string_types

Part of blueprint keystone-py3kcompat

Change-Id: I5022259cfd648ba2680aabbb0fbc403f10c5dc7e
Merge "Sync several modules from oslo-incubator"
Merge "Sync with global requirements"
Merge "remove unused LOG"
Merge "Use six.string_types instead of basestring"