DEV: Store smoke tests failure image in a dedicated tmp folder.

lib/tasks/smoke_test.rake

@@ -26,6 +26,9 @@ task "smoke:test" do
     request.basic_auth(ENV['AUTH_USER'], ENV['AUTH_PASSWORD'])
   end
 
+  dir = 'tmp/smoke-test-screenshots'
+  FileUtils.mkdir_p(dir) unless Dir.exists?(dir)
+
   start = Time.now
   while true
     response = Net::HTTP.start(uri.hostname, uri.port, use_ssl: uri.scheme == 'https') do |http|