MDL-39489 behat: Updating to 2.6 moodlehq/behat-extension tag

Also solving new problem after Behat
2.5 upgrade.

composer.json

@@ -8,6 +8,6 @@
     "require-dev": {
         "phpunit/phpunit": "3.7.*",
         "phpunit/dbUnit": "1.2.*",
-        "moodlehq/behat-extension": "1.25.6"
+        "moodlehq/behat-extension": "1.26.*"
     }
 }

lib/tests/behat/behat_hooks.php

@@ -32,6 +32,7 @@
 use Behat\Behat\Event\SuiteEvent as SuiteEvent,
     Behat\Behat\Event\ScenarioEvent as ScenarioEvent,
     Behat\Behat\Event\StepEvent as StepEvent,
+    Behat\Mink\Exception\DriverException as DriverException,
     WebDriver\Exception\NoSuchWindow as NoSuchWindow,
     WebDriver\Exception\UnexpectedAlertOpen as UnexpectedAlertOpen,
     WebDriver\Exception\UnknownError as UnknownError,
@@ -143,14 +144,16 @@ public function before_scenario($event) {
             throw new coding_exception('Behat only can modify the test database and the test dataroot!');
         }
 
+        $moreinfo = 'More info in ' . behat_command::DOCS_URL . '#Running_tests';
+        $driverexceptionmsg = 'Selenium server is not running, you need to start it to run tests that involve Javascript. ' . $moreinfo;
         try {
             $session = $this->getSession();
         } catch (CurlExec $e) {
             // Exception thrown by WebDriver, so only @javascript tests will be caugth; in
             // behat_util::is_server_running() we already checked that the server is running.
-            $moreinfo = 'More info in ' . behat_command::DOCS_URL . '#Running_tests';
-            $msg = 'Selenium server is not running, you need to start it to run tests that involve Javascript. ' . $moreinfo;
-            throw new Exception($msg);
+            throw new Exception($driverexceptionmsg);
+        } catch (DriverException $e) {
+            throw new Exception($driverexceptionmsg);
         } catch (UnknownError $e) {
             // Generic 'I have no idea' Selenium error. Custom exception to provide more feedback about possible solutions.
             $this->throw_unknown_exception($e);

lib/tests/behat/behat_transformations.php

@@ -56,6 +56,9 @@ class behat_transformations extends behat_base {
      * @return string The string with the arguments fixed.
      */
     public function arg_replace_slashes($string) {
+        if (!is_scalar($string)) {
+            return $string;
+        }
         return str_replace('\"', '"', $string);
     }
 
@@ -67,6 +70,9 @@ public function arg_replace_slashes($string) {
      * @return string
      */
     public function arg_replace_nasty_strings($argument) {
+        if (!is_scalar($argument)) {
+            return $argument;
+        }
         return $this->replace_nasty_strings($argument);
     }