When I ran this command (in my Windows environment), if I entered text that failed validation, I saw this (for example, when entering '$$' for a branch name):

prompt:
Name of the feature::  $$
error:   Invalid input for
Name of the feature:
error:   Names can only contain dashes, 0-9, and a-z
prompt:
Name of the feature::

Somewhere in the flow, we're sending the Name prompt twice.  Note also the double colon in the first and last prompts, but not in the second one.