test: disable test-subrepo-git.t in python2 + chg

I am a couple of days in try to debug that at it seems minor enough with enough
other priority to simply disable it for now.

Differential Revision: https://phab.mercurial-scm.org/D11253

tests/test-subrepo-git.t

@@ -1,5 +1,20 b''
 #require git
 
+# XXX-CHG When running with python2 + chg this test tend to get stuck and end up
+# as a time-out error. My effort to reproduce this outside of the CI failed. The
+# test itself seems to pass fine, but never "complete". Debugging it is slow and
+# tedious. This as a bad impact on the development process as most CI run end up
+# wasting abotu 1h until that one fails.
+#
+# Pierre-Yves David, Augie Fackler and Raphaël Gomès all agreed to disable this
+# case in that specific case until we figure this out (or we drop python2 o:-) )
+
+#if no-py3 chg
+  $ echo 'skipped: this test get stuck on the CI with python2 + chg. investigation needed'
+  $ exit 80
+#endif
+
+
 make git commits repeatable
 
   $ cat >> $HGRCPATH <<EOF