Remove Unused local variable $original_path from /core/lib/Drupal/Core/Path/AliasManager.php

Sure, $source needed here, because could not be defined as used in second part of condition

PS: phpstorm could be wrong, I've filed issue to their tracker WI-19665

Nope phpstorm is not wrong $source is always defined again by the second part of the if statement as this will always be executed because the condition is an OR.

To be honest I think the code would be more readable if the was this

      $source = array_search($path, $this->lookupMap[$langcode]);
      if (!isset($this->lookupMap[$langcode]) || !$source) {

Much more readable

Great job!

Committed and pushed to 8.x. Thanks!