Properly ignore flake8 F811 redefinition errors

Question

I realized that we were actually already ignoring redefinition errors, but we were doing it incorrectly. I think flake8's API must have changed recently because this previously worked on my laptop until I updated flake8. Before, things like # noqa: ignore=501 worked, but then the syntax changed to # noqa: E501. fixed this in #3651, but didn't realize that 811 was actually F811, not E811. This PR fixes that.

Features

• Properly ignore flake8 F811 redefinition errors
• Fix bug causing trailing whitespace characters to be ignored
• They should now properly raise "W291: trailing whitespace"
• Don't use git features unavailable in older versions
• Fixes #3199
• Previously, spack flake8 didn't work with git 1.7.1, the default on CentOS 6
• Ignore more directives
• list_url
• provides()
• conflicts()
• resource()
• Add unit tests

该提问来源于开源项目：spack/spack

Answer 1

While I'm here I might as well fix #3199. Shouldn't be difficult to get spack flake8 working with older versions of git.