run-tests: use byte strings for inserted output
We were inserting str on Python 3 which resulted in mixed
str/bytes types on the list. This would later blow up when
trying to write str to the .err file opened in bytes mode.
Differential Revision: https://phab.mercurial-scm.org/D7222
$ hg init
$ echo a > a
$ hg ci -Am t
adding a
$ hg mv a b
$ hg ci -Am t1
$ hg debugrename b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3
$ hg mv b a
$ hg ci -Am t2
$ hg debugrename a
a renamed from b:37d9b5d994eab34eda9c16b195ace52c7b129980
$ hg debugrename --rev 1 b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3