feature #7733 Documented the new ConsoleEvents::ERROR event (javiereguiluz)

This PR was merged into the master branch.

Discussion
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Documented the new ConsoleEvents::ERROR event

This fixes #7704.

I propose to add this small section ... and refactor it in 3.4 to remove `Console::EXCEPTION` and move its description to the new `Console::ERROR`.

Commits
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ad2bb86 Documented the new ConsoleEvents::ERROR event

Author: xabbuh

components/console/events.rst

@@ -86,6 +86,10 @@ C/C++ standard.::
 The ``ConsoleEvents::EXCEPTION`` Event
 --------------------------------------
 
+.. versionadded:: 3.3
+    The ``ConsoleEvents::EXCEPTION`` event was deprecated in Symfony 3.3. Use
+    the ``ConsoleEvents::ERROR`` event instead.
+
 **Typical Purposes**: Handle exceptions thrown during the execution of a
 command.
 
@@ -113,6 +117,19 @@ Listeners receive a
         $event->setException(new \LogicException('Caught exception', $exitCode, $event->getException()));
     });
 
+The ``ConsoleEvents::ERROR`` Event
+----------------------------------
+
+.. versionadded:: 3.3
+    The ``ConsoleEvents::ERROR`` event was introduced in Symfony 3.3.
+
+**Typical Purposes**: Handle exceptions thrown during the execution of a
+command.
+
+This event is an improved version of the ``ConsoleEvents::EXCEPTION`` event,
+because it can handle every exception thrown during the execution of a command,
+including those triggered from event listeners.
+
 The ``ConsoleEvents::TERMINATE`` Event
 --------------------------------------