Add Python style checker (flake8) and fix existing violations

[felker]

Most of the PEP 8 recommendations are adopted, including the restrictive 79 character limit per line. Ignored/excluded PEP 8 rules are listed in the [flake8] block of setup.cfg and are described in the adjacent comments.

Travis CI is now configured to run the linter as a preliminary build stage for all builds. If flake8 emits a warning or error, the main install+test build stage will be aborted, and Travis will report the overall build as failed.

Detailed summary

• Selects the flake8 Python module as the tool to be used for checking Python style. This command line utility wraps the PyFlakes, pycodestyle (formerly pep8), and McCabe (for checking code complexity) tools.
  • flake8 is probably the most popular Python linter, and it was straightforward to setup these lightweight checks.
  • Pylint is also a popular tool, but I am less familiar with it.
• Adds linting rules to setup.cfg
  • The configuration could alternatively be stored in hidden file .flake8, if preferred.
• Applies autopep8 tool to all Python files currently in the project
• Manually fixes remaining flake8 error code violations that autopep8 was unable to correct and fixed some ugly indentation that resulted from the automated conversion.
  • Tried to eliminate the "considered deprecated" usages of \ line continuation characters in favor of explicit delimiters () and hanging indents.

To-do

• [ ] Switch Jenkins server and workspace
• [ ] Add flake8 check to Jenkins builds
• [ ] Continue updating Travis CI YAML. Should apt-based addons be replaced by virtualenv?
• [ ] Refactor the heavily-duplicated parts of the code

[buildbot-princeton]

Can one of the admins verify this patch?

[buildbot-princeton]

Can one of the admins verify this patch?

[felker]

Add to whitelist