`ucw.fb.read`:: Read error (e.g., the `read` syscall has failed or the stream is write-only)
`ucw.fb.seek`:: Seek error (e.g., file not seekable, or a seek behind EOF)
`ucw.fb.tmp`:: Creation of temporary file failed
`ucw.fb.read`:: Read error (e.g., the `read` syscall has failed or the stream is write-only)
`ucw.fb.seek`:: Seek error (e.g., file not seekable, or a seek behind EOF)
`ucw.fb.tmp`:: Creation of temporary file failed