In templates/classic/html/issue.index.html :
head_title and body_title are not translated with :
List of issues - Show All
List of issues - Show Unassigned

I think that is because in :

<span metal:fill-slot="body_title"
tal:omit-tag="python:1"                               
                          i18n:translate="">List of issues 
   <span tal:condition="request/dispname"
          tal:replace="python:' - %s' %
request.dispname" />

List of issues, and the result of request.dispname are
in separate msgid .po strings.

So, we have to put two spans inside another span (as in
bug 1439927).
By the way, tal:replace and i18n:translate seem to be
incompatible :

   1. Compilation failed
      roundup.cgi.TAL.TALDefs.I18NError: i18n:translate
and tal:replace are mutually exclusive, at line 10,
column 148

Traceback (most recent call last):
  File
"/usr/lib/python2.3/site-packages/roundup/cgi/client.py",
line 729, in renderContext
    result = pt.render(self, None, None, **args)
  File
"/usr/lib/python2.3/site-packages/roundup/cgi/templating.py",
line 312, in render
    raise PageTemplate.PTRuntimeError, \
PTRuntimeError: Page Template issue.index.html has errors.

So we have to put tal:content tal:omit-tag


So, with :

<span metal:fill-slot="body_title"                    
                                                      
      tal:omit-tag="python:1"><span i18n:translate="" 
                                                      
                                
tal:omit-tag="python:1"                               
                                                      
   tal:content="string:List of issues"/><span
tal:omit-tag                                          
               tal:condition="request/dispname"> -
<span                                                 
                      i18n:translate=""               
                                                      
                         tal:content="request/dispname" 
                           tal:omit-tag="python:1"
/></span></span>


it works.

For head_title, I didn't succeed because of :
i18n:name="tracker"