rollback sidekiq to 2.8.0. Fail build if exception in runner

Gemfile

@@ -29,7 +29,7 @@ gem 'haml-rails'
 # Background jobs
 gem 'slim'
 gem 'sinatra', :require => nil
-gem 'sidekiq'
+gem 'sidekiq', '2.8.0'
 # Scheduled
 gem 'whenever', require: false

Gemfile.lock

@@ -191,7 +191,7 @@ GEM
     settingslogic (2.0.8)
     shoulda-matchers (1.3.0)
       activesupport (>= 3.0.0)
-    sidekiq (2.9.0)
+    sidekiq (2.8.0)
       celluloid (~> 0.12.0)
       connection_pool (~> 1.0)
       multi_json (~> 1)
@@ -274,7 +274,7 @@ DEPENDENCIES
   sass-rails (~> 3.2.3)
   settingslogic
   shoulda-matchers
-  sidekiq
+  sidekiq (= 2.8.0)
   sinatra
   slim
   stamp

lib/runner.rb

@@ -103,6 +103,12 @@ class Runner
     end
     @process.exit_code == 0
+
+  rescue => e
+    # return false if any exception occurs
+    @output << e.message
+    false
+
   ensure
     @tmp_file.rewind
     @output << GitlabCi::Encode.encode!(@tmp_file.read)