Attach connection errors to socket

Raising the errors would crash the current thread. As this thread
contains the Eventmachine, that would influence other connections
as well. Attaching the errors to the connection and reading them
after the connection was closed ensures that the thread stays
alive while handling the errors in the main thread of the current
request.

app/models/runner.rb

@@ -50,8 +50,9 @@ class Runner < ApplicationRecord
       # initializing its Runner::Connection with the given event loop. The Runner::Connection class ensures that
       # this event loop is stopped after the socket was closed.
       event_loop = Runner::EventLoop.new
-      @strategy.attach_to_execution(command, event_loop, &block)
+      socket = @strategy.attach_to_execution(command, event_loop, &block)
       event_loop.wait
+      raise socket.error if socket.error.present?
     rescue Runner::Error => e
       e.execution_duration = Time.zone.now - starting_time
       raise