Port build identification from default branch.
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 97ce8cd..56e70e6 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1462,6 +1462,9 @@
SET_SYS_FROM_STRING("subversion",
Py_BuildValue("(ssz)", "CPython", branch,
svn_revision));
+ SET_SYS_FROM_STRING("_mercurial",
+ Py_BuildValue("(szz)", "CPython", _Py_hgidentifier(),
+ _Py_hgversion()));
SET_SYS_FROM_STRING("dont_write_bytecode",
PyBool_FromLong(Py_DontWriteBytecodeFlag));
SET_SYS_FROM_STRING("api_version",