Typescript Transpiler Plugin Sublime Text 3

import sublime, sublime_plugin
import subprocess
import os
import datetime

class Transpiler:
    def __init__(self, fn):
        self.__filename = fn
        self.__validate_file = None
        self.__returncode = 0
        self.status = None
        self.now = datetime.datetime.now()
        self.hour = self.now.strftime("%H:%M:%S")

    def __is_valid(self):
        if self.__filename.endswith('.ts'):
            return True
        else:
            return -1

    def __run(self):
        process = subprocess.Popen("tsc --p ../ts/",
                                    stdout=subprocess.PIPE,
                                    shell=True)
        out, err = process.communicate()
        return (out.decode('ascii'), process.returncode)

    def __get_error (self, error):
        error = error[0]
        return error[:error.find(':')]

    def run(self):
        self.__validate_file = self.__is_valid()
        if self.__validate_file == True:
            execution = self.__run()
            if ('error' not in execution[0]) and (execution[1] == 0):
                self.status = "✓ Transpilation sucessfully at {}".format(self.hour)
            else:
                self.status = "✗ Transpilation failed at {} - {}".format(self.hour, self.__get_error(execution))
        else:
            self.status = ""

class EventListener(sublime_plugin.EventListener):
    def on_post_save_async(self, view):
        transpiler = Transpiler(view.file_name())
        transpiler.run()
        view.set_status('transpiler', transpiler.status)