As a result of simplifying configuration sync directory configuration we have also deprecated config_get_config_directory(), CONFIG_SYNC_DIRECTORY and drupal_install_config_directories().
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The constant CONFIG_SYNC_DIRECTORY has no replacement because it is not necessary anymore.
I guess we should just remove lines from 43 to 49 because $settings['config_directories'] doesn't exist anymore.
CONFIG_SYNC_DIRECTORY constant is deprecated but it is used in source code.
This variable was deprecated, see this change registry: The sync directory is defined in $settings and not $config_directories .
I guess we should just remove lines from 43 to 49 because $settings['config_directories'] doesn't exist anymore.