having no user or passwd specified in conf file gives unclear error message
If the user has not specified a default username/password in the hammer conf files, nor have they specified in on the command line, the error message just says " 'undefined method `clear' for nil:NilClass'". This is part of the stack trace when it fails to make http call.
A better error message is appropriate. (If this is general issue w/ hammer and not specific to csv, change project of this issue.)