Remove pycodestyle

All the formatting-related warnings from `pycodestyle` are covered by
Black, and almost all of the remaining ones are covered by `pylint`.
Based on that, remove `pycodestyle` so that we don't have to maintain
another set of configuration.

More details on warnings/errors covered by `pycodestyle` below.

---

Here's the big list of pycodestyle error/warning codes:
https://pycodestyle.readthedocs.io/en/latest/intro.html#error-codes. They are
broken down into following categories:

1. Indentation
2. Whitespace
3. Blank line
4. Import
5. Line Length
6. Runtime
7. Deprecation warning
8. Statement

Out of the above, 1-5 are purely formatting related so we don't needd to care
about them. 6 is runtime issues like syntax error that are hard to miss (even
mypy will complain about these). 7 is about deprecation warnings. Half of them
don't apply to us since we only support Python 3.5+ and the other half is
covered by `pylint`.

That leaves us with the "E7*" codes, that pycodestyle groups under "Statement"
heading. After verifying each of them, the only ones that is really not covered
by either Black or Pylint is the following:

*  E731   do not assign a lambda expression, use a def

This sole check does not seem worth keeping another tool.

1 files changed, 0 insertions, 1 deletions

diff --git a/tox.ini b/tox.ini
index d8fa3e984..bd07e9e6c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -131,7 +131,6 @@ commands_pre =
     {envpython} setup.py build_ext --inplace
 
 commands =
-    pycodestyle {posargs}
     pylint {posargs: src tests}
 deps =
     -rrequirements/requirements.txt