Catch Payment Processor Exception if thrown when registering via back…

… office participant registration

Make changes as per Matt's and Eileen's comments

CRM/Event/Form/Participant.php

@@ -1256,10 +1256,14 @@ public function submit($params) {
 
       // CRM-15622: fix for incorrect contribution.fee_amount
       $paymentParams['fee_amount'] = NULL;
-      $result = $payment->doPayment($paymentParams);
-
-      if (is_a($result, 'CRM_Core_Error')) {
-        CRM_Core_Error::displaySessionError($result);
+      try {
+        $result = $payment->doPayment($paymentParams);
+      }
+      catch (\Civi\Payment\Exception\PaymentProcessorException $e) {
+        // @todo un comment the following line out when we are creating a contribution before we get to this point
+        // see dev/financial#53 about ensuring we create a pending contribution before we try processing payment
+        // CRM_Contribute_BAO_Contribution::failPayment($contributionID);
+        CRM_Core_Session::singleton()->setStatus($e->getMessage());
         CRM_Utils_System::redirect(CRM_Utils_System::url('civicrm/contact/view/participant',
           "reset=1&action=add&cid={$this->_contactId}&context=participant&mode={$this->_mode}"
         ));