Remove the is_dir check from the ClassLoader

refs #5786

library/Icinga/Application/ClassLoader.php

@@ -29,18 +29,9 @@ class ClassLoader
      * @param   string  $directory
      *
      * @return  $this
-     * @throws  ProgrammingError
      */
     public function registerNamespace($namespace, $directory)
     {
-        if (!is_dir($directory)) {
-            throw new ProgrammingError(
-                'Directory "%s" for namespace "%s" does not exist',
-                $directory,
-                $namespace
-            );
-        }
-
         $this->namespaces[$namespace] = $directory;
 
         return $this;

test/php/library/Icinga/Application/ClassLoaderTest.php

@@ -107,13 +107,4 @@ EOD;
         $o = new \My\Library\TestStruct();
         $this->assertTrue($o->testFlag());
     }
-
-    /**
-     * @expectedException Icinga\Exception\ProgrammingError
-     */
-    public function testNonexistingDirectory()
-    {
-        $loader = new ClassLoader();
-        $loader->registerNamespace('My\\Library', '/trullalla/123');
-    }
 }