# The error `asset.missing`

**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/assets/_cache.py`:
  - what happened: `the experiment needs {…} ({…}), which {…}`
  - what to do: `Run: '{…}'`
- in `mime/saved/_folder.py`:
  - what happened: `the experiment needs {…}, the asset {…}{…}, which travels as a reference and is not in the folder`
  - what to do: `Run: '{…}'`
- in `mime/saved/_terms.py`:
  - what happened: `{…}, which travels as the reference {…}, is not placed in the folder: {…}`
  - what to do: `the folder's lock names a place outside it: save the experiment again from its script, built.save(folder)` or `move the file in its place away, or fetch the asset, then ''{…}'' again`

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