fails:File.open opens a file with a file descriptor d and a block
fails:File.open with a block propagates StandardErrors produced by close
slow:File.open on a FIFO opens it as a normal file
fails:File.open creates an unnamed temporary file with File::TMPFILE
fails:File.open accepts extra flags as a keyword argument and combine with a string mode
fails:File.open accepts extra flags as a keyword argument and combine with an integer mode
