Make check_subsystem_order work in distcheck builds.

diff --git a/scripts/maint/practracker/includes.py b/scripts/maint/practracker/includes.py
index e08fd0d7060ef6a283592bd374adf515ed4d699a..ff465bde63465103b432ddc86decd33d9c7175ee 100755 (executable)
--- a/scripts/maint/practracker/includes.py
+++ b/scripts/maint/practracker/includes.py
@@ -270,6 +270,11 @@ def open_or_stdin(fname):
         return open(fname)
 
 def check_subsys_file(fname, uses_dirs):
+    if not uses_dirs:
+        # We're doing a distcheck build, or for some other reason there are
+        # no .may_include files.
+        return False
+
     uses_dirs = { normalize_srcdir(k) : { normalize_srcdir(d) for d in v }
                   for (k,v) in uses_dirs.items() }
     uses_closure = closure(uses_dirs)