Add missing requirement: web.py
add flake8 checks to teuthology

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
(cherry picked from commit 27c9eb8f81dc25c7b50bfb77d4d2d4ab4d136fb6)
Make teuthology.locker a module
Fix undefined name errors
Remove unused imports
Remove unused variables
Don't redefine variable
Add '# noqa' to suppress a linter error

Fixing this would require some more significant changes... and tempt me
with rewriting every module in the directory.