tox: Use pre-commit for pep8 target

pre-commit is an effective linter runner. No need to duplicate things.
We are able to remove our homegrown "is this valid JSON" check by using
the one built into pre-commit. Beautiful!

Change-Id: I89398d4a1c5d4e7205f5f9c499cba0b4ff90fa46
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

tox.ini

@@ -107,43 +107,29 @@ extras =
 commands =
   bash tools/mypywrap.sh {posargs}
 
+[testenv:pep8]
+description =
+  Run style checks.
+deps =
+  pre-commit
+extras =
+commands =
+  pre-commit run --all-files --show-diff-on-failure
+
+[testenv:autopep8]
+extras =
+deps =
+  pre-commit
+commands =
+  pre-commit run --all-files --show-diff-on-failure autopep8
+
 [testenv:codespell]
 description =
   Run codespell to check spelling.
 deps =
   pre-commit
 commands =
-  pre-commit run codespell --all-files --show-diff-on-failure
-
-[testenv:pep8]
-description =
-  Run style checks.
-deps =
-  {[testenv]deps}
-  {[testenv:codespell]deps}
-  autopep8
-extras =
-commands =
-  {[testenv:mypy]commands}
-  {[testenv:codespell]commands}
-  # check if autopep8 would alter the formatting but don't actually change it
-  # so we can gate on this in the ci
-  autopep8 --exit-code --max-line-length=79 --diff -r nova doc setup.py
-  # since autopep8 only tries to make minimal changes to conform to pep8 we still need to run
-  # our hacking and flake8 check to keep our existing code style consistent.
-  # The full list of issues addressable by autopep8 can be found here
-  # https://pypi.org/project/autopep8/#features
-  bash tools/flake8wrap.sh {posargs}
-  # Check that all JSON files don't have \r\n in line.
-  bash -c "! find doc/ -type f -name *.json | xargs grep -U -n $'\r'"
-  # Check that all included JSON files are valid JSON
-  bash -c '! find doc/ -type f -name *.json | xargs -t -n1 python -m json.tool 2>&1 > /dev/null | grep -B1 -v ^python'
-
-[testenv:autopep8]
-extras =
-deps = autopep8
-commands =
-  autopep8 --exit-code --max-line-length=79 --in-place -r nova doc setup.py
+  pre-commit run --all-files --show-diff-on-failure codespell
 
 [testenv:fast8]
 description =