minor #8411 Add note about LocaleListener (Steveb-p, javiereguiluz)

This PR was merged into the 3.3 branch.

Discussion
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Add note about LocaleListener

LocaleListener uses information provided by Request object.
Setting your own Listener, which is supposed to change request object locale, without priority results in LocaleListener already having it's locale set up and not reacting at all. This change adds this warning to documentation.

Commits
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531909d Reword
1492f3e Remove information about default priority
52681f4 Fix missing blank line
03de10f Add note about LocaleListener

Author: javiereguiluz

translation/locale.rst

@@ -26,6 +26,13 @@ it::
             $request->setLocale($locale);
         }
 
+.. note::
+
+    The custom listener must be called **before** ``LocaleListener``, which
+    initializes the locale based on the current request. To do so, set your
+    listener priority to a higher value than ``LocaleListener`` priority (which
+    you can obtain running the ``debug:event kernel.request`` command).
+
 Read :doc:`/session/locale_sticky_session` for more information on making
 the user's locale "sticky" to their session.