selenium: 'geckodriver' executable may have wrong permissions

My setup:

• MacOS 10.12.3 virtual env.
• I’ve installed selenium via pip install selenium (3.3.1).
• I’ve installed geckodriver via brew install geckodriver 0.15.0

Trying to run the following code in intelliJ IDE:

from selenium import webdriver
from selenium.webdriver.common.keys import Keys

driver = webdriver.Firefox(executable_path='/usr/local/opt/geckodriver')
driver.get("https://google.com")
elem = driver.find_element_by_name("q")

and Exception is thrown from the 4th line (driver = webdriver...):

Traceback (most recent call last):
  File "/Users/itayb/test/main.py", line 4, in <module>
    driver = webdriver.Firefox(executable_path='/usr/local/opt/geckodriver')
  File "/Users/itayb/test/venv/lib/python2.7/site-packages/selenium/webdriver/firefox/webdriver.py", line 145, in __init__
    self.service.start()
  File "/Users/itayb/test/venv/lib/python2.7/site-packages/selenium/webdriver/common/service.py", line 86, in start
    os.path.basename(self.path), self.start_error_message)
selenium.common.exceptions.WebDriverException: Message: 'geckodriver' executable may have wrong permissions. 


Process finished with exit code 1

must say that the executable_path was added after trying to see some answers here in SO.
The bin file (geckodriver is excute from command line without any problem).
How do I fix that?