Mark python as configured even if we couldn't find the includes or libraries. We try to forge ahead anyway, and saying we didn't just causes more problems. We should consider erroring out in this case, instead, but for now this change is minimally disruptive.

src/tools/python.jam

@@ -798,17 +798,15 @@ local rule configure ( version ? : cmd-or-prefix ? : includes * : libraries ? :
     }
 
     # Anything left to compute?
-    if $(includes) && $(libraries)
-    {
-        .configured = true ;
-    }
-    else
+    if ! ( $(includes) && $(libraries) )
     {
         version ?= $(fallback-version) ;
         version ?= 2.5 ;
         exec-prefix ?= $(prefix) ;
         compute-default-paths $(target-os) : $(version) : $(prefix:E=) ;
     }
+    
+    .configured = true ;
 
     if ! $(interpreter-cmd)
     {