py: set_modtime: print warning if fail

Author: scivision

+stdlib/private/py_set_modtime.m

@@ -4,7 +4,8 @@
   s = py.os.stat(p);
   py.os.utime(p, py.tuple(s.st_atime, utc));
   ok = true;
-catch
+catch e
+  warning(e.identifier, "%s", e.message)
   ok = false;
 end