setup.py: keep Python 2.3 compatibility

Though we only support Python 2.4 or greater, we should keep setup.py
compatible with earlier versions on the syntactic level. Otherwise
people will simply get a SyntaxError when trying to install Mercurial
with an old version of Python. With this change, the setup.py file can
be imported with Python 2.3 and we then issue a friendly error message
when we detect that Python is too old.

setup.py

@@ -145,8 +145,8 b" if os.path.isdir('.hg'):"
     if version.endswith('+'):
         version += time.strftime('%Y%m%d')
 elif os.path.exists('.hg_archival.txt'):
-    kw = dict([t.strip() for t in l.split(':', 1)]
-              for l in open('.hg_archival.txt'))
+    kw = dict([[t.strip() for t in l.split(':', 1)]
+               for l in open('.hg_archival.txt')])
     if 'tag' in kw:
         version =  kw['tag']
     elif 'latesttag' in kw: