Adding ldappool module dependency as needed by keystone bug #1320997.

Ldappool has MPL license and is needed as part of https://review.openstack.org/#/c/95300/
This module provides pooling of LDAP connections.
In keystone, this is optional dependency similar to python-ldap.

Related-Bug: #1320997

Change-Id: Id03a5f42cdc677e9f1f630341a10f6763b010394
Bump pep8 from 1.5.6 to 1.5.7

Bump pep8 version in an overlapping way, so add pep8 version 1.5.7 and a
subsequent patch will drop pep8 1.5.6.

Pep8 1.5.7 has additional bug fixes

Change-Id: Ic356886984f70992276b49555e1ec7b3d34b000a
Fix sphinx requirement to add overlap

When I63c6159eb23430a181eb20016b35366c2fbbf9f8 was implemented it
didn't include any overlap with the previous required versions,
which causes breakage in the gate while the change is being tested
and until the mirror updates. For completeness add the suggested
overlap back in for now.

Change-Id: I70559a2b6eb961bf1c5fbe8006cd1275c39577b6
Co-Authored-By: Doug Hellmann <doug.hellmann@dreamhost.com>
Merge "Bump pep8 from 1.5.6 to 1.5.7"
Merge "Fix sphinx requirement to add overlap"
Merge "Adding ldappool module dependency as needed by keystone bug #1320997."