class Jekyll::Configuration

def check_plugins(config)

is not an Array.
Raises a Jekyll::Errors::InvalidConfigurationError if the config `plugins`

config - the config hash

Private: Checks if the `plugins` config is a String 
def check_plugins(config)
  return unless config.key?("plugins")
  return if config["plugins"].is_a?(Array)
  Jekyll.logger.error "'plugins' should be set as an array of gem-names, but was: " \
                      "#{config["plugins"].inspect}. Use 'plugins_dir' instead to set " \
                      "the directory for your non-gemified Ruby plugins."
  raise Jekyll::Errors::InvalidConfigurationError,
        "'plugins' should be set as an array, but was: #{config["plugins"].inspect}."
end