The fix is described at http://dev.rubyonrails.org/ticket/9940. Simply edit the plugsin/exception_notification/views/exception_notification/_environment.rhtml file, and change the third line to:
The only difference is that the first *- is changed to -*.
* <%= "%-*s: %s" % [max.length, key, filter_sensitive_post_data_from_env(key, @request.env[key].to_s.strip)] %>
The only difference is that the first *- is changed to -*.