Issue #3188920 by xjm: Make Guzzle exception handling forward-compatible with Guzzle 7

core/includes/install.core.inc

core/modules/aggregator/src/Form/OpmlFeedAdd.php

...gregator/src/Plugin/aggregator/fetcher/DefaultFetcher.php

core/modules/locale/locale.batch.inc

core/modules/media/src/OEmbed/ProviderRepository.php

core/modules/media/src/OEmbed/ResourceFetcher.php

core/modules/media/src/OEmbed/UrlResolver.php

core/modules/media/src/Plugin/media/Source/OEmbed.php

core/modules/system/system.module

core/modules/update/src/UpdateFetcher.php

core/tests/Drupal/Tests/DrupalTestBrowser.php