Fatal error: Uncaught Error: Call to undefined method Guzzle\Common\Collection::fromConfig()

[htrex]

I'm trying to activate the plugin on a fresh WP instance, but I'm receiving the following fatal error

Fatal error: Uncaught Error: Call to undefined method Guzzle\Common\Collection::fromConfig() in /var/www/cuim_wp/wp-content/plugins/wpckan/vendor/silex/ckan_client/src/Silex/ckan/CkanClient.php:33 Stack trace: #0 /var/www/cuim_wp/wp-content/plugins/wpckan/utils/wpckan-api.php(349): Silex\ckan\CkanClient::factory(Array) #1 /var/www/cuim_wp/wp-content/plugins/wpckan/utils/wpckan-utils.php(559): wpckan_api_ping() #2 /var/www/cuim_wp/wp-content/plugins/wpckan/wpckan.php(61): wpckan_validate_settings_read() #3 /var/www/cuim_wp/wp-includes/class-wp-hook.php(286): wpckan->check_requirements('') #4 /var/www/cuim_wp/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(false, Array) #5 /var/www/cuim_wp/wp-includes/plugin.php(453): WP_Hook->do_action(Array) #6 /var/www/cuim_wp/wp-admin/admin-header.php(255): do_action('admin_notices') #7 /var/www/cuim_wp/wp-admin/plugins.php(454): require_once('/var/www/...') #8 {main} thrown in /var/www/cuim_wp/wp-content/plugins/wpckan/vendor/silex/ckan_client/src/Silex/ckan/CkanClient.php on line 33

I suspect that some package is specifying it's dependencies too liberally and composer install could be getting a newer/incompatible package version in some way.
@acorbi @Huyeng could you please commit and push a working composer.lock file?