Add pre-commit to pep8 gate

Flake8 is covered in the pre-commit hooks

Change-Id: I0fc88f0dd641b82c5a3456d687c5958d94667eb0
Signed-off-by: Moisés Guimarães de Medeiros <moguimar@redhat.com>

test-requirements.txt

@@ -7,6 +7,7 @@ pifpaf>=0.10.0 # Apache-2.0
 # Bandit security code scanner
 bandit>=1.6.0,<1.7.0 # Apache-2.0
 stestr>=2.0.0 # Apache-2.0
+pre-commit>=2.6.0 # MIT
 python-memcached>=1.56 # PSF
 pymongo!=3.1,>=3.0.2 # Apache-2.0
 etcd3gw>=0.2.0 # Apache-2.0

tox.ini

@@ -24,16 +24,10 @@ commands =
 [testenv:pep8]
 deps = {[testenv]deps}
 commands =
-  flake8
+  pre-commit run -a
   # Run security linter
   bandit -r oslo_cache -x tests -n5
 
-[testenv:pre-commit]
-deps =
-  pre-commit
-commands =
-  pre-commit run --from-ref HEAD^ --to-ref HEAD
-
 [testenv:venv]
 commands = {posargs}