Implementation of https://stackoverflow.com/a/35293284 for
        https://stackoverflow.com/questions/12848327/
        (Run Selenium on a proxy server that requires authentication.)
        Solution involves creating & adding a Chrome extension on the fly.
        * CHROME-ONLY for now! *

def create_proxy_zip(proxy_string, proxy_user, proxy_pass):
    """ Implementation of https://stackoverflow.com/a/35293284 for
        https://stackoverflow.com/questions/12848327/
        (Run Selenium on a proxy server that requires authentication.)
        Solution involves creating & adding a Chrome extension on the fly.
        * CHROME-ONLY for now! *
    """
    proxy_host = proxy_string.split(':')[0]
    proxy_port = proxy_string.split(':')[1]
    background_js = (
        """var config = {\n"""
        """    mode: "fixed_servers",\n"""
        """    rules: {\n"""
        """      singleProxy: {\n"""
        """        scheme: "http",\n"""
        """        host: "%s",\n"""
        """        port: parseInt("%s")\n"""
        """      },\n"""
        """    }\n"""
        """  };\n"""
        """chrome.proxy.settings.set("""
        """{value: config, scope: "regular"}, function() {"""
        """});\n"""
        """function callbackFn(details) {\n"""
        """    return {\n"""
        """        authCredentials: {\n"""
        """            username: "%s",\n"""
        """            password: "%s"\n"""
        """        }\n"""
        """    };\n"""
        """}\n"""
        """chrome.webRequest.onAuthRequired.addListener(\n"""
        """        callbackFn,\n"""
        """        {urls: ["<all_urls>"]},\n"""
        """        ['blocking']\n"""
        """);""" % (proxy_host, proxy_port, proxy_user, proxy_pass))
    manifest_json = (
        '''{\n'''
        '''"version": "1.0.0",\n'''
        '''"manifest_version": 2,\n'''
        '''"name": "Chrome Proxy",\n'''
        '''"permissions": [\n'''
        '''    "proxy",\n'''
        '''    "tabs",\n'''
        '''    "unlimitedStorage",\n'''
        '''    "storage",\n'''
        '''    "<all_urls>",\n'''
        '''    "webRequest",\n'''
        '''    "webRequestBlocking"\n'''
        '''],\n'''
        '''"background": {\n'''
        '''    "scripts": ["background.js"]\n'''
        '''},\n'''
        '''"minimum_chrome_version":"22.0.0"\n'''
        '''}''')
    lock = threading.RLock()  # Support multi-threaded test runs with Pytest
    with lock:
        try:
            zf = zipfile.ZipFile(PROXY_ZIP_PATH, mode='w')
        except IOError:
            # Handle "Permission denied" on the default proxy.zip path
            abs_path = os.path.abspath('.')
            downloads_path = os.path.join(abs_path, DOWNLOADS_DIR)
            if not os.path.exists(downloads_path):
                os.mkdir(downloads_path)
            zf = zipfile.ZipFile(PROXY_ZIP_PATH_2, mode='w')
        zf.writestr("background.js", background_js)
        zf.writestr("manifest.json", manifest_json)
        zf.close()