--- a/hgext3rd/evolve/obsexchange.py	Tue Mar 07 15:04:58 2017 +0100
+++ b/hgext3rd/evolve/obsexchange.py	Tue Mar 07 15:10:57 2017 +0100
@@ -61,45 +61,6 @@
             kwargs['evo_obscommon'] = common
     return ret
 
-@eh.wrapfunction(exchange, '_pullobsolete')
-def _pullobsolete(orig, pullop):
-    if not obsolete.isenabled(pullop.repo, obsolete.exchangeopt):
-        return None
-    if 'obsmarkers' in pullop.stepsdone:
-        return None
-    wirepull = pullop.remote.capable('_evoext_pullobsmarkers_0')
-    if not wirepull:
-        return orig(pullop)
-    if 'obsolete' not in pullop.remote.listkeys('namespaces'):
-        return None # remote opted out of obsolescence marker exchange
-    tr = None
-    ui = pullop.repo.ui
-    boundaries = obsdiscovery._buildpullobsmarkersboundaries(pullop)
-    if not set(boundaries['heads']) - set(boundaries['common']):
-        obsexcmsg(ui, "nothing to pull\n")
-        return None
-
-    obsexcmsg(ui, "pull obsolescence markers\n", True)
-    new = 0
-
-    if wirepull:
-        obsdata = pullop.remote.evoext_pullobsmarkers_0(**boundaries)
-        obsdata = obsdata.read()
-        if len(obsdata) > 5:
-            msg = "merging obsolescence markers (%i bytes)\n" % len(obsdata)
-            obsexcmsg(ui, msg)
-            tr = pullop.gettransaction()
-            old = len(pullop.repo.obsstore._all)
-            pullop.repo.obsstore.mergemarkers(tr, obsdata)
-            new = len(pullop.repo.obsstore._all) - old
-            obsexcmsg(ui, "%i obsolescence markers added\n" % new, True)
-        else:
-            obsexcmsg(ui, "no unknown remote markers\n")
-        obsexcmsg(ui, "DONE\n")
-    if new:
-        pullop.repo.invalidatevolatilesets()
-    return tr
-
 ###############################################
 ### Support for old legacy exchange methods ###
 ###############################################
@@ -233,6 +194,52 @@
     data = obsfile.read()
     serveronly._pushobsmarkers(peer._repo, data)
 
+# compat-code: _pullobsolete
+#
+# the _pullobsolete function is a core function used to exchange
+# obsmarker with repository that does not support bundle2
+
+@eh.wrapfunction(exchange, '_pullobsolete')
+def _pullobsolete(orig, pullop):
+    if not obsolete.isenabled(pullop.repo, obsolete.exchangeopt):
+        return None
+    if 'obsmarkers' in pullop.stepsdone:
+        return None
+    wirepull = pullop.remote.capable('_evoext_pullobsmarkers_0')
+    if not wirepull:
+        return orig(pullop)
+    tr = None
+    ui = pullop.repo.ui
+    boundaries = obsdiscovery._buildpullobsmarkersboundaries(pullop)
+    if not set(boundaries['heads']) - set(boundaries['common']):
+        obsexcmsg(ui, "nothing to pull\n")
+        return None
+
+    obsexcmsg(ui, "pull obsolescence markers\n", True)
+    new = 0
+
+    msg = ('the remote repository use years old versions of Mercurial and evolve\n'
+           'pulling obsmarker using legacy method\n')
+    ui.warn(msg)
+    ui.warn('(please upgrade your server)\n')
+
+    obsdata = pullop.remote.evoext_pullobsmarkers_0(**boundaries)
+    obsdata = obsdata.read()
+    if len(obsdata) > 5:
+        msg = "merging obsolescence markers (%i bytes)\n" % len(obsdata)
+        obsexcmsg(ui, msg)
+        tr = pullop.gettransaction()
+        old = len(pullop.repo.obsstore._all)
+        pullop.repo.obsstore.mergemarkers(tr, obsdata)
+        new = len(pullop.repo.obsstore._all) - old
+        obsexcmsg(ui, "%i obsolescence markers added\n" % new, True)
+    else:
+        obsexcmsg(ui, "no unknown remote markers\n")
+    obsexcmsg(ui, "DONE\n")
+    if new:
+        pullop.repo.invalidatevolatilesets()
+    return tr
+
 @eh.addattr(wireproto.wirepeer, 'evoext_pullobsmarkers_0')
 def client_pullobsmarkers(self, heads=None, common=None):
     self.requirecap('_evoext_pullobsmarkers_0', _('look up remote obsmarkers'))

--- a/tests/test-simple4server.t	Tue Mar 07 15:04:58 2017 +0100
+++ b/tests/test-simple4server.t	Tue Mar 07 15:10:57 2017 +0100
@@ -73,6 +73,9 @@
   adding file changes
   added 2 changesets with 2 changes to 2 files
   pull obsolescence markers
+  the remote repository use years old versions of Mercurial and evolve
+  pulling obsmarker using legacy method
+  (please upgrade your server)
   (run 'hg update' to get a working copy)
   $ cat ../errors.log
   $ hg push -R ../other
@@ -132,6 +135,9 @@
   adding file changes
   added 1 changesets with 1 changes to [12] files \(\+1 heads\) (re)
   pull obsolescence markers
+  the remote repository use years old versions of Mercurial and evolve
+  pulling obsmarker using legacy method
+  (please upgrade your server)
   2 obsolescence markers added
   (run 'hg heads' to see heads)
   $ cat ../errors.log