Skip unit tests if ArcanistLinter::getCacheVersion throws an ArcanistUsageException

Summary: Fixes T4288

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T4288

Differential Revision: https://secure.phabricator.com/D7913

src/lint/linter/__tests__/ArcanistLinterTestCase.php

@@ -119,6 +119,8 @@ abstract class ArcanistLinterTestCase extends ArcanistPhutilTestCase {
             $caught_exception = true;
           }
         }
+      } else if ($exception instanceof ArcanistUsageException) {
+        $this->assertSkipped($exception->getMessage());
       }
       $exception_message = $exception->getMessage()."\n\n".
                            $exception->getTraceAsString();