Avoid mutable default arguments

[mbeacom]

The goal of this PR is to remove mutable arguments that are defaulted in methods throughout the codebase.

For information on causation and manual steps to resolution, check out:
https://www.quantifiedcode.com/app/issue_class/3P0qV6OB

[Zulko]

Nice ! was it actually done by a robot ??

[tburrows13]

Looks fine. For anyone wondering the purpose of this, see http://stackoverflow.com/questions/1132941/least-astonishment-and-the-mutable-default-argument

[mbeacom]

@Zulko It was indeed! Not really something that I was hiding? 👍 No reason to take the time to go through and manually modify simple, but fairly important best practices that can be automagically fixed. We could have the same service resolve these directly if the integration is setup on the parent repo.

Some of these are fairly trivial to change manually, but should probably start being enforced against the master repo. Thoughts?

What do you think about adding https://www.quantifiedcode.com/ to the repo? It's free for opensource projects!

Unless you want more one-liners to resolve this like apply_to = apply_to or [], but this can lead to failures pending on the passed argument types. Realistically it shouldn't. If you'd prefer that, I'll resubmit with manual changes.

[coveralls]

Coverage increased (+0.07%) to 54.463% when pulling 34db3d3 on mbeacom:autofix/wrapped2_to3_fix-0 into 03fdc2c on Zulko:master.

[tburrows13]

Any reason why this is closed @mbeacom?

[mbeacom]

@Gloin1313 I was uncertain if there were objections to the changes. XD

[ghost]

@mbeacom I definitely see this PR as a enhancement..

[Zulko]

LGTM