Convert 'opts' option to list

- Multiple arguments were not supported for the 'opts' argument. Fix
  this by using a list for arguments, rather than a string
Remove default case from "settings"

- The default settings value of '" "' for 'opts' causes issues.
  Remove this as it's not necessary.
Pretty print exceptions

- Exceptions are displayed using 'error_message' calls, but the output
  value is raw and not encoded correctly. Fix this.
Fix issue where value of 'opts' wasn't checked
Revert "Pretty print exceptions"

This reverts commit d54fe869278868741a311d11729121c0038bc326.

This modification can cause some issues and hence is not yet
ready for prime time. Revert until it's complete.
Merge branch 'bug/205' into development