Google Sheets: friendlier error message in case of an API error and more reliable test connection (#3883)
Google Sheets: friendlier error message in case of an API error and more reliable test connection (#3883)

* Google Sheets: friendlier error message in case of an APIError and more reliable test connection.

* Pleasing the pep8 gods

alexanderlz/redash,getredash/redash,getredash/redash,getredash/redash,getredash/redash,denisov-vlad/redash,denisov-vlad/redash,alexanderlz/redash,denisov-vlad/redash,getredash/redash,alexanderlz/redash,denisov-vlad/redash,alexanderlz/redash,denisov-vlad/redash