Pipe output from Process into GUI

Question

I am writing a PyQt4 based launcher. When clicking a button in the launcher start_tool is called. this function opens an new terminal, executing anoother tool. hence two new windows are openend, the terminal and the newly started tool. I now want to pipe the output of the new terminal into a textedit of the launcher in order to track the errors WITHIN the launcher. I need to be able to operate both the launcher and the started tool at the same time.

I have tried following code, it pipes some output but then an "FATAL IO error: client killed" is thrown and the launcher is killed.

    def f(self, lock, tools):
        try:
            lock.acquire()
            ex = sub.Popen(tools, shell=True,stdout=sub.PIPE,stderr=sub.STDOUT)
            p = os.getpid()
            while True:
                output = ex.stdout.readline().decode()
                if output == '' and ex.poll() is not None:
                    break
                if output:
                        self.console_launcher.insertPlainText(output)
                        QtGui.QApplication.processEvents()
            lock.release()
        except sub.CalledProcessError as e:
            lock.acquire()
            print(e)
            lock.release()
        finally:
            lock.release()

    def start_tool(self):
        lock = mp.Lock()
        tools = ['gnome-terminal --tab -- shells/program.sh']
        p = mp.Process(target=self.f, args=(lock, tools))
        p.start()
        p.join()

I want to pipe the output of Tool B into the Gui of tool A. Both are PyQt4 based apps and need to run separetly.