tests: add missing b prefix in test python in test-issue2137.t

# skip-blame just a b prefix

Differential Revision: https://phab.mercurial-scm.org/D2539

tests/test-issue2137.t

@@ -1,56 +1,56 b''
 https://bz.mercurial-scm.org/2137
 
 Setup:
 
 create a little extension that has 3 side-effects:
 1) ensure changelog data is not inlined
 2) make revlog to use lazyparser
 3) test that repo.lookup() works
 1 and 2 are preconditions for the bug; 3 is the bug.
 
   $ cat > commitwrapper.py <<EOF
   > from mercurial import extensions, node, revlog
   > 
   > def reposetup(ui, repo):
   >     class wraprepo(repo.__class__):
   >         def commit(self, *args, **kwargs):
   >             result = super(wraprepo, self).commit(*args, **kwargs)
   >             tip1 = node.short(repo.changelog.tip())
   >             tip2 = node.short(repo.lookup(tip1))
   >             assert tip1 == tip2
-  >             ui.write('new tip: %s\n' % tip1)
+  >             ui.write(b'new tip: %s\n' % tip1)
   >             return result
   >     repo.__class__ = wraprepo
   > 
   > def extsetup(ui):
   >     revlog._maxinline = 8             # split out 00changelog.d early
   >     revlog._prereadsize = 8           # use revlog.lazyparser
   > EOF
 
   $ cat >> $HGRCPATH <<EOF
   > [extensions]
   > commitwrapper = `pwd`/commitwrapper.py
   > EOF
 
   $ hg init repo1
   $ cd repo1
   $ echo a > a
   $ hg commit -A -m'add a with a long commit message to make the changelog a bit bigger'
   adding a
   new tip: 553596fad57b
 
 Test that new changesets are visible to repo.lookup():
 
   $ echo a >> a
   $ hg commit -m'one more commit to demonstrate the bug'
   new tip: 799ae3599e0e
 
   $ hg tip
   changeset:   1:799ae3599e0e
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     one more commit to demonstrate the bug
   
 
   $ cd ..