convert: fix authormap handling of lines without '='
Unpacking the result from str.split raises ValueError, not IndexError, if the
line does not contain a '='.
initializing destination new repository
Ignoring bad line in author map file authormap.txt: this line is ignored
scanning source...
sorting...
converting...
0 foo
Writing author map file new/.hg/authormap
0
user name=Long User Name
changeset: 0:d89716e88087
tag: tip
user: Long User Name
date: Thu Jan 01 00:00:00 1970 +0000
summary: foo
Ignoring bad line in author map file new/.hg/authormap: this line is ignored
scanning source...
sorting...
converting...
0 foo
0
changeset: 0:d89716e88087
tag: tip
user: Long User Name
date: Thu Jan 01 00:00:00 1970 +0000
summary: foo