ISLANDORA-581 On content model trigered tabs we use module_exists to verify if a module is present and enabled before calling code. We also use module_load_include instead of including directly.

ContentModel.inc

@@ -1475,7 +1475,17 @@ class ContentModel extends XMLDatastream {
                 self::$errors[] = 'Execute Form Handler: file \'' . $path . '\' does not exist.';
               }
               else {
-                require_once($path);
+
+                $file_extension = pathinfo($method->getAttribute('file'), PATHINFO_EXTENSION);
+                $file_path_without_extension = $method->getAttribute('file');
+                /* Only in PHP. This is meant to avoid file path
+                 * concatenation issues.*/
+                $file_path_without_extension = substr($file_path_without_extension, 0, strlen($file_path_without_extension) - (strlen($file_extension) + 1));
+                /* Only try to execute if the module is present, this is
+                 * necessarybecause we go outside of the expected
+                 * 'Drupal Way' and have dynamic dependencies.*/
+                if (module_exists(!empty($module) ? $module : 'fedora_repository')) {
+                  module_load_include($file_extension, !empty($module) ? $module : 'fedora_repository', $file_path_without_extension);
                   $className = $method->getAttribute('class');
                   $methodName = ($method->getAttribute('method'));
                   if (!class_exists($className)) {
@@ -1496,6 +1506,7 @@ class ContentModel extends XMLDatastream {
           }
         }
       }
+    }
 
     return $output;
   }