'Requires Distributions' should include 'babel'

[SpongeTsui]

In the line 24 of file '_gettextutils.py' on version 'oslo.i18n==3.15.2', there is an import statement as 'from babel import localedata'.

Considering that 'babel' is not a standard library for python 2.7, so babel should be included as a requirement for oslo.i18n.

If babel not installed, after the execution of the following commands on a new-installed os:

pip install python-keystoneclient
pip install python-swiftclient

it will fail when using auth version 2.0 and the hints are as follow:
"Failed:
Auth versions 2.0 and 3 require python-keystoneclient, install it or use Auth
version 1.0 which requires ST_AUTH, ST_USER, and ST_KEY environment
variables to be set or overridden with -A, -U, or -K."

and these hints are generated form swiftclient==3.10.0 when executing 'from keystoneclient.v2_0 import client as ksclient' in line 542 of file swiftclient.client.py.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Corey Bryant (corey.bryant)]

I've marked the corresponding upstream projects as affected by this bug in order to get their input.

[Doug Hellmann (doug-hellmann)]

The latest version of oslo.i18n does include babel in its requirements list.

[Corey Bryant (corey.bryant)]

I checked the Ubuntu packages for python(3)-oslo.i18n back to Kilo and they all have python(3)-babel as a dependency, so marking as invalid for the Ubuntu packages.

[Morgan Fainberg (mdrnstm)]

With i18n including the dependency, does Keystoneclient also need it explicitly?