Merge pull request #6188 from MrPetovan/bug/5928-protect-oauthexception

Protect OAuthException declaration to avoid conflict with php-pecl-oauth

library/OAuth1.php

@@ -3,8 +3,10 @@
 
 /* Generic exception class
  */
-class OAuthException extends Exception {
-  // pass
+if (!class_exists('OAuthException', false)) {
+  class OAuthException extends Exception {
+    // pass
+  }
 }
 
 class OAuthConsumer {