xmlmarclint: 'no valid record detected' error
xmlmarclint: 'no valid record detected' error

* Raises importance of 'no valid record detected' case from warning
  to error; otherwise submitting any bad text file would pass the check.

* Cherry-picked from a6b7ede4875ec74d29ff3f9ac93412bcd00783de.

tiborsimko/invenio,tiborsimko/invenio,inveniosoftware/invenio,inveniosoftware/invenio