GCPのdebian上でseleniumのheadless firefoxを試みる
結論を言いますとうまくいきませんでした．
手元のMac上なら動くが，GCP上ではうまく行かず．
以下，やったことの記録．
以下のサイトに習い，geckodriveをインストール．
https://a-zumi.net/selenium-ubuntu-geckodriver/
https://github.com/mozilla/geckodriver/releases
firefoxをインストール．
sudo apt-get install firefox-esr
他にも，mozillaのリポジトリを追加して最新版を追加したり，debファイルを引っ張ってきて，旧版をインストールしたりしたが，結果的にはあまり意味なかった．
python3で以下のように実行．
from selenium import webdriver
from selenium.webdriver.firefox.options import Options
options = Options()
options.add_argument('-headless')
driver = webdriver.Firefox(firefox_options=options)
次のようなエラーが出る．
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/opt/bitnami/python/lib/python3.6/site-packages/selenium/webdriver/firefox/webdriver.py", line 170, in __init__
keep_alive=True)
File "/opt/bitnami/python/lib/python3.6/site-packages/selenium/webdriver/remote/webdriver.py", line 156, in __init__
self.start_session(capabilities, browser_profile)
File "/opt/bitnami/python/lib/python3.6/site-packages/selenium/webdriver/remote/webdriver.py", line 251, in start_session
response = self.execute(Command.NEW_SESSION, parameters)
File "/opt/bitnami/python/lib/python3.6/site-packages/selenium/webdriver/remote/webdriver.py", line 320, in execute
self.error_handler.check_response(response)
File "/opt/bitnami/python/lib/python3.6/site-packages/selenium/webdriver/remote/errorhandler.py", line 242, in check_response
raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.SessionNotCreatedException: Message: Unable to find a matching set of capabilities
試行錯誤の上，capabilities の marionette を False にするとcapability のエラーが無くなった．
from selenium import webdriver
from selenium.webdriver.common.desired_capabilities import DesiredCapabilities
from selenium.webdriver.firefox.options import Options
options = Options()
options.add_argument('-headless')
desiredcapabilities = DesiredCapabilities.FIREFOX.copy()
desiredcapabilities['marionette'] = False
driver = webdriver.Firefox(capabilities=desiredcapabilities, firefox_options=options)
しかし，まだ以下のようなエラーが出る．
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/opt/bitnami/python/lib/python3.6/site-packages/selenium/webdriver/firefox/webdriver.py", line 187, in __init__
self.binary, timeout)
File "/opt/bitnami/python/lib/python3.6/site-packages/selenium/webdriver/firefox/extension_connection.py", line 52, in __init__
self.binary.launch_browser(self.profile, timeout=timeout)
File "/opt/bitnami/python/lib/python3.6/site-packages/selenium/webdriver/firefox/firefox_binary.py", line 73, in launch_browser
self._wait_until_connectable(timeout=timeout)
File "/opt/bitnami/python/lib/python3.6/site-packages/selenium/webdriver/firefox/firefox_binary.py", line 104, in _wait_until_connectable
"The browser appears to have exited "
selenium.common.exceptions.WebDriverException: Message: The browser appears to have exited before we could connect. If you specified a log_file in the FirefoxBinary constructor, check it for details.
以下のようにすると，geckodriverのログを出力できる．
from selenium import webdriver
from selenium.webdriver.common.desired_capabilities import DesiredCapabilities
from selenium.webdriver.firefox.firefox_binary import FirefoxBinary
desiredcapabilities = DesiredCapabilities.FIREFOX.copy()
desiredcapabilities['marionette'] = False
binary = FirefoxBinary(log_file=open("geckodriver.log", "wb"))
binary.add_command_line_options('-headless')
driver = webdriver.Firefox(capabilities=desiredcapabilities, firefox_binary=binary)
ログを見ると，以下のような内容．
XPCOMGlueLoad error for file /usr/lib/firefox-esr/libmozgtk.so:
/usr/lib/x86_64-linux-gnu/libpangoft2-1.0.so.0: undefined symbol: FcConfigReference
Couldn't load XPCOM.
このエラーがどうしても解決できずに断念．
chromeに切り替えることにした．
2018/10/8 追記
Chromeに変えても同様の問題が発生し，散々色々やった挙げ句，解決せず途方に暮れた．
結局，vmをbitnamiのdjangostacでやっていたのが問題だったようで，vmをbitnamiを使わず新たに立ち上げ直してやってみたらすんなり行って，拍子抜けした．
