tweakview: conform to pep8
@jbicha I've not applied any linter to this, all of this was done manually with suggestions from pep8 so there might be certain styles this project follows which may go against pep8, we can get rid of them from this MR.
If this is the right way to go, I'd like to go through the whole project since I came across other files too which have certain trivial issues, thus the WIP.
- remove unused imports
- fix pep8 issues
Edited by Jeremy Bicha