tests: b prefixes on some inline python in test-convert-cvs.t

# skip-blame just b prefixes

Differential Revision: https://phab.mercurial-scm.org/D3488

tests/test-convert-cvs.t

@@ -522,8 +522,8 b' Commit messages of version 1.2 - 1.4 use'
 
   $ mkdir -p cvsrepo/transcoding
   $ python <<EOF
-  > fp = open('cvsrepo/transcoding/file,v', 'w')
-  > fp.write(('''
+  > fp = open('cvsrepo/transcoding/file,v', 'wb')
+  > fp.write((b'''
   > head	1.4;
   > access;
   > symbols
@@ -570,7 +570,7 b' Commit messages of version 1.2 - 1.4 use'
   > 
   > 1.4
   > log
-  > @''' + u'\u3042'.encode('cp932') + ''' (cp932)
+  > @''' + u'\u3042'.encode('cp932') + b''' (cp932)
   > @
   > text
   > @1
@@ -582,7 +582,7 b' Commit messages of version 1.2 - 1.4 use'
   > 
   > 1.3
   > log
-  > @''' + u'\u3042'.encode('euc-jp') + ''' (euc-jp)
+  > @''' + u'\u3042'.encode('euc-jp') + b''' (euc-jp)
   > @
   > text
   > @d4 1
@@ -591,7 +591,7 b' Commit messages of version 1.2 - 1.4 use'
   > 
   > 1.2
   > log
-  > @''' + u'\u3042'.encode('utf-8') +  ''' (utf-8)
+  > @''' + u'\u3042'.encode('utf-8') +  b''' (utf-8)
   > @
   > text
   > @d3 1