title: logback: controlling the formatting of exception stacktraces
body: <p>I'm using Logback 1.0.13 on a Scala/Play 2.2.0 app.
  Existing config looks like:</p>
  
  <pre><code>  &lt;appender name="FILE" class="ch.qos.logback.core.FileAppender"&gt;
      &lt;file&gt;${application.home}/logs/application.log&lt;/file&gt;
      &lt;encoder&gt;
       &lt;pattern&gt;%date [%level][%logger{1}][%thread{1}] %message%xException%n&lt;/pattern&gt;
      &lt;/encoder&gt;
    &lt;/appender&gt;
  </code></pre>
  
  <p>I'm looking if there's a way to configure it so exception traceback lines have a customized separator.  Instead of </p>
  
  <pre><code>play.api.Configuration$$anon$1: Configuration error[Cannot connect to database [default]]
  at play.api.Configuration$.play$api$Configuration$$configError(Configuration.scala:92) ~[play_2.10-2.2.0.jar:2.2.0]
  at play.api.Configuration.reportError(Configuration.scala:570) ~[play_2.10-2.2.0.jar:2.2.0]
  at play.api.db.BoneCPPlugin$$anonfun$onStart$1.apply(DB.scala:252) ~[play-jdbc_2.10-2.2.0.jar:2.2.0]
  </code></pre>
  
  <p>I'd like to put some chars in front of each line like this:</p>
  
  <pre><code>play.api.Configuration$$anon$1: Configuration error[Cannot connect to database [default]]
  &gt;&gt;&gt; at play.api.Configuration$.play$api$Configuration$$configError(Configuration.scala:92) ~[play_2.10-2.2.0.jar:2.2.0]
  &gt;&gt;&gt; at play.api.Configuration.reportError(Configuration.scala:570) ~[play_2.10-2.2.0.jar:2.2.0]
  &gt;&gt;&gt; at play.api.db.BoneCPPlugin$$anonfun$onStart$1.apply(DB.scala:252) ~[play-jdbc_2.10-2.2.0.jar:2.2.0]
  </code></pre>