public function findNamespace($namespace)
    {
        $allNamespaces = $this->getNamespaces();
        $expr = preg_replace_callback('{([^:]+|)}', function ($matches) { return preg_quote($matches[1]).'[^:]*'; }, $namespace);
        $namespaces = preg_grep('{^'.$expr.'}', $allNamespaces);

        if (empty($namespaces)) {
            $message = sprintf('There are no commands defined in the "%s" namespace.', $namespace);

            if ($alternatives = $this->findAlternatives($namespace, $allNamespaces)) {
                if (1 == count($alternatives)) {
                    $message .= "\n\nDid you mean this?\n    ";
                } else {
                    $message .= "\n\nDid you mean one of these?\n    ";
                }

                $message .= implode("\n    ", $alternatives);
            }

            throw new CommandNotFoundException($message, $alternatives);
        }

        $exact = in_array($namespace, $namespaces, true);
        if (count($namespaces) > 1 && !$exact) {
            throw new CommandNotFoundException(sprintf("The namespace \"%s\" is ambiguous.\nDid you mean one of these?\n%s", $namespace, $this->getAbbreviationSuggestions(array_values($namespaces))), array_values($namespaces));
        }

        return $exact ? $namespace : reset($namespaces);
    }