Useful under the circumstance when the person running the script is not
in fact the RelCo for the next release, as it has already been the case
before. Saves one having to manually reassign all the newly created
tickets to the actual RelCo. Conversely, if it is the same person just
omit the new argument and the RelCo user name will be used to connect to
JIRA.

Note that the function validating user names is only applied to RelCo
ones. This is intentional, JIRA itself will complain if the submitter is
not authorised to create ENSCORESW tickets.