py3: use bytes.endswith() instead of bytes[n]

contrib/python3-whitelist

@@ -2,6 +2,7 b' test-abort-checkin.t'
 test-add.t
 test-addremove-similar.t
 test-addremove.t
+test-alias.t
 test-amend-subrepo.t
 test-amend.t
 test-ancestor.py

mercurial/pathutil.py

@@ -226,7 +226,7 b' def canonpath(root, cwd, myname, auditor'
             if cwd != root:
                 canonpath(root, root, myname, auditor)
                 relpath = util.pathto(root, cwd, '')
-                if relpath[-1] == pycompat.ossep:
+                if relpath.endswith(pycompat.ossep):
                     relpath = relpath[:-1]
                 hint = (_("consider using '--cwd %s'") % relpath)
         except error.Abort: