As I [embarrassingly] discovered in 272938@main, if a directory exists with the same name as an expectation file in the location it would normally be, run-webkit-tests crashes when it tries to read it. I subsequently fixed the error in 272944@main. It seems like this should be an easy fix -- just catching an error (this one was IsADirectoryError) when the expectations files are accessed.
<rdar://problem/121076361>