# The error `load.stage-writer`

**environment**: something the run needs is missing or different where it runs (a package, a file, a device, the network): the error names what to install, fetch or attach.

Where MIME gives it, with what its message says happened and what its action says to do (`{…}` is filled in from the experiment):

- in `mime/saved/_folder.py`:
  - what happened: `the stage was written by stage writer {…}, and this MIME writes versions {…}`
  - what to do: `install the MIME that saved it, 'pip install mime-engine=={…}', or build the experiment from its script and save it again: 'built.save(folder)'`

Reading an error and reaching its full traceback: [reading an error](../reading_errors.md). Every code: [the index](index.md).