Python Selenium Gecko Hatası

# -*- coding: UTF-8 -*-

from selenium import webdriver
from selenium.webdriver.firefox.options import Options


url = str(input("enter url : "))

options =   Options()
options.headless = True

br  = webdriver.Firefox(options=options) 
br.get(url)

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/common/service.py", line 76, in start
    stdin=PIPE)
  File "/usr/lib/python3.7/subprocess.py", line 800, in __init__
    restore_signals, start_new_session)
  File "/usr/lib/python3.7/subprocess.py", line 1551, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'geckodriver': 'geckodriver'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "pythondeneme.py", line 12, in <module>
    br  = webdriver.Firefox(options=options) 
  File "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/firefox/webdriver.py", line 164, in __init__
    self.service.start()
  File "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/common/service.py", line 83, in start
    os.path.basename(self.path), self.start_error_message)
selenium.common.exceptions.WebDriverException: Message: 'geckodriver' executable needs to be in PATH.