tests: allow running doctests selectively on Python 3

Currently most doctests fail on Python 3, but I want to add some.

tests/test-doctest.py

@@ -1,46 +1,52
 # this is hack to make sure no escape characters are inserted into the output
 
 from __future__ import absolute_import
 
 import doctest
 import os
 import sys
+
+ispy3 = (sys.version_info[0] >= 3)
+
 if 'TERM' in os.environ:
     del os.environ['TERM']
 
-def testmod(name, optionflags=0, testtarget=None):
+# TODO: migrate doctests to py3 and enable them on both versions
+def testmod(name, optionflags=0, testtarget=None, py2=True, py3=False):
+    if not (not ispy3 and py2 or ispy3 and py3):
+        return
     __import__(name)
     mod = sys.modules[name]
     if testtarget is not None:
         mod = getattr(mod, testtarget)
     doctest.testmod(mod, optionflags=optionflags)
 
 testmod('mercurial.changegroup')
 testmod('mercurial.changelog')
 testmod('mercurial.dagparser', optionflags=doctest.NORMALIZE_WHITESPACE)
 testmod('mercurial.dispatch')
 testmod('mercurial.encoding')
 testmod('mercurial.formatter')
 testmod('mercurial.hg')
 testmod('mercurial.hgweb.hgwebdir_mod')
 testmod('mercurial.match')
 testmod('mercurial.minirst')
 testmod('mercurial.patch')
 testmod('mercurial.pathutil')
 testmod('mercurial.parser')
 testmod('mercurial.revsetlang')
 testmod('mercurial.smartset')
 testmod('mercurial.store')
 testmod('mercurial.subrepo')
 testmod('mercurial.templatefilters')
 testmod('mercurial.templater')
 testmod('mercurial.ui')
 testmod('mercurial.url')
 testmod('mercurial.util')
 testmod('mercurial.util', testtarget='platform')
 testmod('hgext.convert.convcmd')
 testmod('hgext.convert.cvsps')
 testmod('hgext.convert.filemap')
 testmod('hgext.convert.p4')
 testmod('hgext.convert.subversion')
 testmod('hgext.mq')