# The error `env.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/env/_check.py`:
  - what happened: `{…} {…}, pinned by {…}, is not installed`
  - what to do: `rebuild the environment from the pinned requirements ('mime modal' writes a script that does)`
- in `mime/errors/_missing.py`:
  - what happened: `{…} is not installed, and {…} requires it (MIME could not import {…})`
  - what to do: `install it with MIME's requirements: '{…}'; or the package alone: pip install {…}`

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