When the S3 repository plugin runs into problems, the errors that are displayed are not descriptive.

Reproduction steps (requires an AWS account):

1. Configure an S3 repository instance; it is unimportant to create buckets.
2. On your Moodle server, disable automatic time sync and change the time to be several hours before the current time.
3. Attempt to use the S3 repository.
   • Moodle will throw a moodle_exception, and tell you "Error while communicating with the repository '<yourreponamehere>'".
   • The error code will be "errorwhilecommunicatingwith", which doesn't tell you what actually happened.
4. Create a PHP file in your Moodle directory, s3test.php, with the following contents:

   <?php

   require_once("repository/s3/S3.php");

   $key_a = "your access key here";

   $key_s = "your secret access key here";

   S3::setAuth($key_a, $key_s);

   $buckets = S3::listBuckets(true);

   echo '<pre>';

   print_r($buckets);

   echo '</pre>';

   ?>

   • Amend the file with your access and secret access keys.
5. Access the file you created in a web browser.
   • Observe that the S3 library gave you a meaningful message that was not passed up into Moodle, along the lines of
     Warning: S3::listBuckets(): [RequestTimeTooSkewed] The difference between the request time and the current time is too large.