message: Include the filename when we encounter EOF
diff: @@ -181,7 +181,9 @@ Status FileBlockCache::Read(const string& filename, size_t offset, size_t n,
  // The requested offset is at or beyond the end of the file. This can
  // happen if `offset` is not block-aligned, and the read returns the last
  // block in the file, which does not extend all the way out to `offset`.
  - return errors::OutOfRange("EOF at offset ", offset);
  + return errors::OutOfRange("EOF at offset ", offset, " in file ", filename,
  + " at position ", pos, "with data size ",
  + data.size());
  }
  auto begin = data.begin();
  if (offset > pos) {
  