dirs: convert PyString to PyBytes
PyStringObject was renamed to PyBytes in Python 3 along with the
corresponding PyString* functions and macros. PyString* doesn't
exist in Python 3. But PyBytes* is an alias to PyString in Python 2.
So rewrite PyString* to PyBytes* for Python 2/3 dual compatibility.
$ 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