Fix flake8 errors in anticipation of flake8.

Change-Id: I7c713f95eb974d5998d2be50722df7d6f64a234e
Switch to flake8+hacking.

Remove a bunch of local custom scripts. Replace with configurable
external tools.
Use local hacking checks for nova specifics.

Change-Id: I75a01375ba0ec36d2ff05abc47abe0a3f225eda5
Merge "Fix flake8 errors in anticipation of flake8."
Merge "Switch to flake8+hacking."