@type check_return_t() ::
  :ok
  | :skipped
  | {:warn, output :: binary()}
  | {:error, output :: binary(), remedy :: binary()}

Valid return values from a check.

• :ok - The check succeeded with no problems.
• :skipped - Doctor checks for files in .medic/skipped/ to skip a check. Custom checks could return this to notify Doctor that they chose internally to skip the check.
• {:warn, output} - The check generated warnings, but does not stop Doctor from proceeding.
• {:error, output, remedy} - The check failed. Output may be stdout and/or stderr generated from shell commands, or custom error output to show to the user. The remedy will by copied into the local paste buffer.