The function get_linkified_textline() wraps the URLs found in
wraps URLs found in text lines with HTML tags to make
them clickable.

>>> from mklists.linkify import _return_textline_linkified

Lines already containing HREF tags are left untouched:

>>> line = """Line with <a href="http://example.org">HREF tags</a>.\n"""
>>> _return_textline_linkified(line)
'Line with <a href="http://example.org">HREF tags</a>.\n'

