When any of the vendor packages are not present, there should be a correct error in the error log

Ensure that when the vendor packages aren't present that we are writing to the error log successfully. Right now the error does not write to the error log, so it's harder to pin point what the issue would be.

Example: https://github.com/EvanHerman/plugin-check/blob/main/class-plugin-check.php#L300-L303

We should be using `error_log()`.