Adjusted error handling based on Googler feedback [(#693)](GoogleCloudPlatform/python-docs-samples#693)

Author: ryanmats

samples/snippets/load_data_from_gcs.py

@@ -54,7 +54,7 @@ def wait_for_job(job):
         job.reload()
         if job.state == 'DONE':
             if job.error_result:
-                raise RuntimeError(job.error_result)
+                raise RuntimeError(job.errors)
             return
         time.sleep(1)