fixed multiple style guide violations

app/controllers/concerns/common_behavior.rb

@@ -1,5 +1,5 @@
 module CommonBehavior
-  def create_and_respond(options = {}, &block)
+  def create_and_respond(options = {})
     @object = options[:object]
     respond_to do |format|
       if @object.save

app/controllers/concerns/submission_parameters.rb

@@ -2,8 +2,8 @@ module SubmissionParameters
   include FileParameters
 
   def reject_illegal_file_attributes!(submission_params)
-    if exercise = Exercise.find_by(id: submission_params[:exercise_id])
-      submission_params[:files_attributes].try(:reject!) do |index, file_attributes|
+    if Exercise.exists?(id: submission_params[:exercise_id])
+      submission_params[:files_attributes].try(:reject!) do |_, file_attributes|
         file = CodeOcean::File.find_by(id: file_attributes[:file_id])
         file.nil? || file.hidden || file.read_only
       end

app/controllers/execution_environments_controller.rb

@@ -24,7 +24,7 @@ class ExecutionEnvironmentsController < ApplicationController
   end
 
   def execute_command
-    @docker_client = DockerClient.new(execution_environment: @execution_environment, user: current_user)
+    @docker_client = DockerClient.new(execution_environment: @execution_environment)
     render(json: @docker_client.execute_arbitrary_command(params[:command]))
   end
 

app/controllers/sessions_controller.rb

@@ -9,7 +9,7 @@ class SessionsController < ApplicationController
   skip_before_action :verify_authenticity_token, only: :create_through_lti
 
   def create
-    if user = login(params[:email], params[:password], params[:remember_me])
+    if login(params[:email], params[:password], params[:remember_me])
       redirect_back_or_to(:root, notice: t('.success'))
     else
       flash.now[:danger] = t('.failure')

app/controllers/submissions_controller.rb

@@ -72,7 +72,7 @@ class SubmissionsController < ApplicationController
   end
 
   def set_docker_client
-    @docker_client = DockerClient.new(execution_environment: @submission.execution_environment, user: current_user)
+    @docker_client = DockerClient.new(execution_environment: @submission.execution_environment)
   end
   private :set_docker_client
 

app/helpers/application_helper.rb

@@ -42,7 +42,7 @@ module ApplicationHelper
     Kramdown::Document.new(markdown).to_html.html_safe
   end
 
-  def row(options={}, &block)
+  def row(options = {}, &block)
     content_tag(:div, class: 'attribute-row row') do
       label_column(options[:label]) + value_column(options[:value], &block)
     end
@@ -65,7 +65,7 @@ module ApplicationHelper
   end
   private :translation_present?
 
-  def value_column(value, &block)
+  def value_column(value)
     content_tag(:div, class: 'col-sm-9') do
       block_given? ? yield : symbol_for(value)
     end

app/mailers/user_mailer.rb

@@ -4,7 +4,7 @@ class UserMailer < ActionMailer::Base
     mail(subject: t('mailers.user_mailer.activation_needed.subject'), to: user.email)
   end
 
-  def activation_success_email(user)
+  def activation_success_email(*)
   end
 
   def reset_password_email(user)

app/models/concerns/user.rb

@@ -13,7 +13,7 @@ module User
   end
 
   ROLES.each do |role|
-    define_method("#{role}?") { self.try(:role) == role }
+    define_method("#{role}?") { try(:role) == role }
   end
 
   def external?

app/models/submission.rb

@@ -7,6 +7,8 @@ class Submission < ActiveRecord::Base
 
   belongs_to :exercise
 
+  delegate :execution_environment, to: :exercise
+
   scope :final, -> { where(cause: 'submit') }
   scope :intermediate, -> { where.not(cause: 'submit') }
 
@@ -24,10 +26,6 @@ class Submission < ActiveRecord::Base
     ancestors.merge(descendants).values
   end
 
-  def execution_environment
-    exercise.execution_environment
-  end
-
   [:download, :render, :run, :test].each do |action|
     filename = FILENAME_URL_PLACEHOLDER.gsub(/\W/, '')
     define_method("#{action}_url") do