Print redis config file if saving failed (#1272)

If saving the Redis settings fails due to a write error, the desired
configuration file content is now displayed so that the user can deploy
it manually (Same behavior as with database configuration).

For that a catch block is introduced on the `NotWritableError` that is
added to `IniWriter::write()` in
Icinga/icingaweb2#5404.

Refs Icinga/icingaweb2#5404
Resolves #1269

Author: jrauh01

application/forms/RedisConfigForm.php

@@ -20,6 +20,8 @@
 use ipl\Validator\PrivateKeyValidator;
 use ipl\Validator\X509CertValidator;
 use Throwable;
+use Zend_Config_Exception;
+use Zend_Form_Decorator_Abstract;
 use Zend_Validate_Callback;
 
 class RedisConfigForm extends ConfigForm
@@ -537,6 +539,17 @@ public function onSuccess()
 
         try {
             $connectionConfig->saveIni();
+        } catch (NotWritableError | Zend_Config_Exception $e) {
+            $this->addDecorator('ViewScript', array(
+                'viewModule'   => 'default',
+                'viewScript'   => 'showConfiguration.phtml',
+                'errorMessage' => $e->getMessage(),
+                'configString' => $connectionConfig,
+                'filePath'     => $connectionConfig->getConfigFile(),
+                'placement'    => Zend_Form_Decorator_Abstract::PREPEND
+            ));
+
+            return false;
         } catch (Throwable $e) {
             $this->addError($e->getMessage());
             Logger::error($e->getMessage());