Exec conversions expect a tuple with an expected set of keys.

The expected keys are:

- command (string, required)
   The command to run in the script.

- env (tuple, optional)
  Any environment variables that should be set in the script.
  The env tuple is converted using the same rules as the env converter.

- args (tuple, optional
  Any command line arguments for the command line.
  The arguments are converted using the same rules as the flags converter.

- Functions and Modules are ignored.