Merge pull request #567 from wp-cli/check-version

Check wp-includes/version.php before loading WP

diff --cc php/WP_CLI/Runner.php
index dacbd30,4c57380..abce204
--- 1/php/WP_CLI/Runner.php
--- 2/php/WP_CLI/Runner.php
+++ b/php/WP_CLI/Runner.php
@@@ -268,8 -268,28 +268,28 @@@ class Runner 
                WP_CLI::set_logger( $logger );
        }
  
+       private function check_wp_version() {
+               if ( !is_readable( ABSPATH . 'wp-includes/version.php' ) ) {
+                       WP_CLI::error(
+                               "This does not seem to be a WordPress install.\n" .
+                               "Pass --path=`path/to/wordpress` or run `wp core download`." );
+               }
+ 
+               include ABSPATH . 'wp-includes/version.php';
+ 
+               $minimum_version = '3.4';
+ 
+               if ( version_compare( $wp_version, $minimum_version, '<' ) ) {
+                       WP_CLI::error(
+                               "WP-CLI needs WordPress $minimum_version or later to work properly. " .
+                               "The version currently installed is $wp_version.\n" .
+                               "Try running `wp core download --force`."
+                       );
+               }
+       }
+ 
        public function before_wp_load() {
 -              list( $args, $assoc_args, $runtime_config ) = \WP_CLI::$configurator->parse_args(
 +              list( $args, $assoc_args, $runtime_config ) = \WP_CLI::get_configurator()->parse_args(
                        array_slice( $GLOBALS['argv'], 1 ) );
  
                list( $this->arguments, $this->assoc_args ) = self::back_compat_conversions(