Good! I worked effectively a whole day with new version of Ubuntu, PHP 7.0 and MySQL 5.7.
What large surprize it was for me when I discovered next morning that MySQL service can not be started. Moreover it said nothing about the reason except:
Fatal error: Uncaught exception 'Google_Auth_Exception' with message 'Error refreshing the OAuth2 token, message: '{ "error" : "invalid_grant" }'' in /includes/Google/Auth/OAuth2.php:330
.
A few days of testing, experiments, “googling” Internet, and miscellaneous shamanic dances with a tambourine around “Google APIs Client Library for PHP” source code and the sample example of its usage did not allow me to make even a little step forward. Trying various variants with service-account.php (recreate service account, replacing private key file, trying other, default service account with client secret loading from JSON file) did not help and I still was on the same place with the same error. That was funny to resolve finally this issue and smile to myself, how the small mistake at very begin may cost a lot of time to fix it.
update_core
capability is used to decide, if user can update core WordPress file using built-in WordPress upgrade feature or not. What do you think?
Thoughts are just thoughts, while they are not confirmed by practice and strong experiment. Thus, I decided to check this obviouse guess, satisfy my curiosity and investigate, how and for what purpose WordPress uses update_core capability really. Result of my little investigation will be shown to you below.