Drop support for legacy Python 2

[hugovk]

Fixes #194.

[pietermarsman]

Hi @hugovk, thanks for the PR! Our policy is to merge PR's with develop. I changed the base branch from master to develop but this causes a couple of merge conflicts, so I changed it back. Could you make sure that you branch of from develop?

[hugovk]

Yes, I'll have a look.

Do you merge to develop to master for releases?

I recommend setting the default branch to develop in the repo settings, that way all new PRs go against that.

You should also mention to make it against develop in a PR template and contributing doc.

• https://help.github.com/en/articles/about-issue-and-pull-request-templates
• https://help.github.com/en/articles/setting-guidelines-for-repository-contributors

[pietermarsman]

This looks incredible thorough.

I will keep looking for additional things that could or should be included in this PR.

[pietermarsman]

I understand that removing explicit inheritence of object is possible since this is the default in Python3. However, I prefer that the inheritance stays explicit cause it's more consistent.

[pietermarsman]

Do you merge to develop to master for releases?

I recommend setting the default branch to develop in the repo settings, that way all new PRs go against that.

You should also mention to make it against develop in a PR template and contributing doc.

• https://help.github.com/en/articles/about-issue-and-pull-request-templates
• https://help.github.com/en/articles/setting-guidelines-for-repository-contributors

Yes, that's how we do it. And I totally agree that having the master as the default branch is causing unnecessary amounts of work. I've just put this issue on the todo list for a owner of the pdfminer organisation (#304).

[hugovk]

Please see PR #305, against develop.