Enhance compatabilty with newer Neutron branches while maintaining
compatability with stable/queens Neutron, and improve the build/test
process. Highlights include:
* Eliminate unneeded requirements and test-requirements, and update
remaining ones to match upstream stable/queens Neutron.
* Use pip directly instead of the tox_install.sh script to install
dependencies, as is done on newer upstream branches.
* Use stestr directly instead of ostestr to run UTs, as is done in newer
upstream branches.
* Specify basepython as python2.7 for pep8, cover, functional and
dsvm-functional jobs, in case a python3 version of tox is used.
* Fix pep8 issues that result in failures with the versions of hacking
and flake8 used by Neutron's stable/rocky through stable/train
branches. These changes are not necessary with the hacking and
flake8 versions used in stable/queens, but we want to minimize code
differences across our currently supported stable branches.
* Enable flake8-import-order and fix all the pep8 issues that it
uncovered, particularly with order and grouping of import
statements.
* Update pep8 configuration in tox.ini to more closely match upstream
Neutron, and fix resulting issues. Remaining ignored checks that
should be fixed but haven't been are marked with REVISIT in tox.ini.
* Update devstack scripts with proper branches and repository URLs.
Change-Id: I538b8c95c61a09d834be4b7c28a3becf2f3e6a50
ca82a36cb1