Fix Ruby warnings, thanks for the reminder @nateberkopec

lib/sidekiq.rb

@@ -171,6 +171,7 @@ module Sidekiq
   def self.default_retries_exhausted=(prok)
     @default_retries_exhausted = prok
   end
+  @default_retries_exhausted = ->(job, ex) { }
   def self.default_retries_exhausted
     @default_retries_exhausted
   end

lib/sidekiq/scheduled.rb

@@ -46,6 +46,7 @@ module Sidekiq
         @enq = (Sidekiq.options[:scheduled_enq] || Sidekiq::Scheduled::Enq).new
         @sleeper = ConnectionPool::TimedStack.new
         @done = false
+        @thread = nil
       end
 
       # Shut down this instance, will pause until the thread is dead.

lib/sidekiq/web.rb

@@ -63,10 +63,6 @@ module Sidekiq
         @views ||= VIEWS
       end
 
-      def session_secret=(secret)
-        @session_secret = secret
-      end
-
       attr_accessor :app_url, :session_secret, :redis_pool
       attr_writer :locales, :views
     end

lib/sidekiq/web/action.rb

@@ -78,6 +78,7 @@ module Sidekiq
     end
 
     def initialize(env, block)
+      @_erb = false
       @env = env
       @block = block
       @@files ||= {}

lib/sidekiq/web/helpers.rb

@@ -52,7 +52,7 @@ module Sidekiq
     end
 
     def display_custom_head
-      @head_html.join if @head_html
+      @head_html.join if defined?(@head_html)
     end
 
     # Given a browser request Accept-Language header like

lib/sidekiq/web/router.rb

@@ -88,7 +88,7 @@ module Sidekiq
         {} if path == matcher
       else
         if path_match = path.match(matcher)
-          params = Hash[path_match.names.map(&:to_sym).zip(path_match.captures)]
+          Hash[path_match.names.map(&:to_sym).zip(path_match.captures)]
         end
       end
     end

test/test_cli.rb

@@ -342,7 +342,7 @@ class TestCli < Sidekiq::Test
       end
 
       after do
-        File.unlink @tmp_log_path if File.exists? @tmp_log_path
+        File.unlink @tmp_log_path if File.exist? @tmp_log_path
       end
 
       it 'shuts down the worker' do
@@ -377,7 +377,7 @@ class TestCli < Sidekiq::Test
       end
 
       after do
-        File.unlink @tmp_log_path if File.exists? @tmp_log_path
+        File.unlink @tmp_log_path if File.exist? @tmp_log_path
       end
 
       describe 'with backtrace' do