py3: pass bytes from extension to ui.write() in test-revlog-mmapindex.t

This makes the test pass on Python 3.

Differential Revision: https://phab.mercurial-scm.org/D1674

tests/test-revlog-mmapindex.t

@@ -1,55 +1,56 b''
 create verbosemmap.py
   $ cat << EOF > verbosemmap.py
   > # extension to make util.mmapread verbose
   > 
   > from __future__ import absolute_import
   > 
   > from mercurial import (
   >     extensions,
+  >     pycompat,
   >     util,
   > )
   > 
   > def extsetup(ui):
   >     def mmapread(orig, fp):
-  >         ui.write("mmapping %s\n" % fp.name)
+  >         ui.write(b"mmapping %s\n" % pycompat.bytestr(fp.name))
   >         ui.flush()
   >         return orig(fp)
   > 
   >     extensions.wrapfunction(util, 'mmapread', mmapread)
   > EOF
 
 setting up base repo
   $ hg init a
   $ cd a
   $ touch a
   $ hg add a
   $ hg commit -qm base
   $ for i in `$TESTDIR/seq.py 1 100` ; do
   > echo $i > a
   > hg commit -qm $i
   > done
 
 set up verbosemmap extension
   $ cat << EOF >> $HGRCPATH
   > [extensions]
   > verbosemmap=$TESTTMP/verbosemmap.py
   > EOF
 
 mmap index which is now more than 4k long
   $ hg log -l 5 -T '{rev}\n' --config experimental.mmapindexthreshold=4k
   mmapping $TESTTMP/a/.hg/store/00changelog.i
   100
   99
   98
   97
   96
 
 do not mmap index which is still less than 32k
   $ hg log -l 5 -T '{rev}\n' --config experimental.mmapindexthreshold=32k
   100
   99
   98
   97
   96
 
   $ cd ..