PHP warning when attempting to autoload a directory that does not exist

[philipnewcomer]

When attempting to autoload from a directory that does not exist, a warning is generated on line 22 ($scanned_dir = scandir( $directory );):

Warning: scandir(/nas/content/staging/cnvbillkristol/wp-content/mu-plugins/app/src): failed to open dir: No such file or directory in /nas/content/staging/cnvbillkristol/wp-content/mu-plugins/app/vendor/aaronholbrook/autoload/autoload.php on line 21

Warning: scandir(): (errno 13): Permission denied in /nas/content/staging/cnvbillkristol/wp-content/mu-plugins/app/vendor/aaronholbrook/autoload/autoload.php on line 21

The autoload script should check to make sure the directory exists before scanning it, and should fail gracefully if it does not.