Trivial flake8 fixes for envisage.ui.single_project

[kitchoi]

These are all the trivial flake8 fixes I have done before I realized that the package may be scheduled for removal (see #266).

They are pretty easy to do. If the flake8 fixes don't go in, we might still want to update setup.cfg to reference #269 anyway.

[kitchoi]

@rahulporuri Should I close this and just update the setup.cfg with a reference separately or is this easy enough to be reviewed?

[rahulporuri]

It's easy enough to be reviewed but it'll just be one more commit before we possibly remove all of the code. I'm sorry for the confusion but it might just be better to discuss #327 and then update setup.cfg or any other solution.

[kitchoi]

No problem. I did not spend a lot of time on actually flaking the thing: I spent more time understanding the issues surrounding whether single_project can be removed, which is probably worthwhile anyway.
Closing (I don't want to let PRs go stale, especially ones that touch a lot of files, it is easy to restore if needed).