Implement code formatting and style checking tools

[Ryan J Ollos]

(from comment:93:ticket:12130)

In the release checklist, reindent is used to fix indentation. ​​pypi:reindent doesn't support Python 3. It appears it's just packaged ​reindent.py from the Python Core. I've emailed the package owner to see if I can get maintainership to update it for Python 3.5+.

Use formatting and style checking tools such as:

• ​autopep8
• ​pycodestyle

Other candidates are:

• ​black
• ​flake8
• ​autoflake8
• ​pylint

Implement ignore rules, as needed, in setup.cfg. Example:

[pycodestyle]
max-line-length = 80
ignore = E126, E127, E128, E129, E131, E241, E731

Format code to remove all warnings and errors.

Add a Makefile command make check-code, which executes the style check tool and contrib/jinja2checker.py. The tool can be run before submitting a "pull request" and before releases.

Revise as needed:

• TracDev/CodingStyle
• TracDev/DevelopmentWorkflow
• TracDev/ReleaseChecklist
• TracDev/SubmittingPatches
• TracDev/UnitTests
• TracDev/FunctionalTests

make status echoes the version of ​pypi:coverage, but the tool isn't integrated into our development process, as far as I'm aware. It's use should be documented, or remove it from make status.

$ make status

Python: /Users/rjollos/.pyenv/shims/python

  Package        Version
  ----------------------------------------------------------------------------
  Python       : 3.6.10 (default, Jan 27 2020, 16:14:13)
               : [GCC 4.2.1 Compatible Apple LLVM 11.0.0 (clang-1100.0.33.17)]
  Setuptools   : 46.4.0
  Pip          : 20.1.1
  Wheel        : 0.34.2
  Jinja2       : 2.11.2
  Babel        : 2.8.0
  sqlite3      : 2.6.0 (3.28.0)
  PySqlite     : not installed
  PyMySQL      : 0.9.3
  Psycopg2     : 2.8.5 (dt dec pq3 ext lo64)
  SVN bindings : 1.15.0 (under development)
  Mercurial    : 5.4
  Pygments     : 2.6.1
  Textile      : 4.0.1
  Pytz         : 2020.1
  Docutils     : 0.16
  Selenium     : 3.141.0
  LXML         : 4.5.1
  coverage     : 5.1

Variables:
...

Consider adding a requirements-dev.txt for installing all development requirements.