Flake8 exceptions are incomplete

[Anselmoo]

Describe the bug

Currently, git commits can be rejected by getting the following log message.

> git -c user.useConfigOnly=true commit --quiet --allow-empty-message --file - -S
Skipped 7 files
./keras_tuner/engine/trial.py:46:19: N805 first argument of a method should be named 'self'
./keras_tuner/engine/trial.py:65:21: N805 first argument of a method should be named 'self'
Please fix the code style issue.

This is related due to missing exceptions in:

https://github.com/keras-team/keras-tuner/blob/41693aacd4440faacca4165e4d15cde53d5570cc/setup.cfg#LL31-L47C9

Moreover, it might be a good idea to refactor the code partially. Like

    def to_proto(status):
        ts = keras_tuner_pb2.TrialStatus

becomes

    @staticmethod
    def to_proto(status):
        ts = keras_tuner_pb2.TrialStatus

To Reproduce

 flake8 .

provides:

./keras_tuner/tuners/sklearn_tuner.py:139:23: N803 argument name 'X' should be lowercase
./keras_tuner/tuners/sklearn_tuner.py:154:33: N803 argument name 'X' should be lowercase
./keras_tuner/tuners/sklearn_tuner.py:160:14: N806 variable 'X_train' in function should be lowercase
./keras_tuner/tuners/sklearn_tuner.py:162:14: N806 variable 'X_test' in function should be lowercase
./keras_tuner/engine/trial.py:46:19: N805 first argument of a method should be named 'self'
./keras_tuner/engine/trial.py:65:21: N805 first argument of a method should be named 'self'
./keras_tuner/engine/conditions.py:63:21: N804 first argument of a classmethod should be named 'cls'

Expected behavior

 flake8 .

provides:

Additional context

Currently fixes: #777

Would you like to help us fix it?