python binary name is hardcoded, but
we need to sed it in during installation

https://bugs.gentoo.org/show_bug.cgi?id=487706

--- a/lib/pychess/Players/engineNest.py
+++ b/lib/pychess/Players/engineNest.py
@@ -70,9 +70,9 @@ backup = """
 <engines version="%s">
     <engine protocol="cecp" protover="2" binname="PyChess.py">
         <meta><country>dk</country></meta>
-        <vm binname="python"><args><arg name='0' value="-u"/></args></vm></engine>
+        <vm binname="@PYTHON@"><args><arg name='0' value="-u"/></args></vm></engine>
     <engine protocol="cecp" protover="2" binname="shatranj.py">
-        <vm binname="python"><args><arg name='0' value="-u"/></args></vm>
+        <vm binname="@PYTHON@"><args><arg name='0' value="-u"/></args></vm>
         <args><arg name='0' value='-xboard'/></args></engine>
     <engine protocol="cecp" protover="2" binname="gnuchess">
         <meta><country>us</country></meta>